Of course this topic is difficult to answer or confirm or prove. The best way by far is proving it to yourself through experience.
Personally being on this track i found the best and easiest way to build belief or confidence is taking the time to learn to astral travel. All "ghosts", entities, weirdness and seemingly supernatural stuff that somehow seems to effect the physical 3rd dimensional word occurs in the 4th dimensional astral plane, which lies very close to the physical (as we know it) 3D plane and can influence it directly depending.
Firstly to answer your question. Sleep paralysis and the strange buzzing or vibrating sound or sensation is the beginning of potential conscious "controllable" astral travel. We astral travel unconsciously or unknowing every night which is what dreams are.
In the higher 4th dimensional astral its possible to manifest any thought or desire. If you are untrained in doing this consciously your mind automatically manifests a "dream" environment in your part of the astral (where space doesnt exist like in 3d, only time) to protect you from weirdness.
So you are in a dream without control or real consciousness (unlike what happens in the more advanced lucid dream which is the prequel to real astral travel) and this protects you from getting out into the real astral proper zone where shit gets interesting or scary depending on your knowledge and readiness.
Anyways, sometimes the potential breakthrough point for conscious astral travel (like sleep paralysis) can be scary or terrifying as a safety mechanism to spur the conscious mind to abort the process through fear (and thus energy to awaken the mind) if your mind, your higher self, your greater spiritual being etc decides your are not ready or you would be to fearful of the real experience. Thats the cause fear when you reach that point.
For example, I had the same shit for years until i learnt, studied and decided through intent to astral travel and when i got there i could reach that point and perform the action with zero fear. That sleep paralysis point of breakthrough was no longer fearful, not because i would decide to be scared through some intellectual reason of now understanding what it meant, but instead there inherent fear was no longer there at all as opposed to deciding not to be fearful, if that makes sense...
There can also be other things effecting you negatively however, that become more obvious when you reach that breakthrough point. Remember when you reach that point its basically the same as deep meditation. Its the raising of consciousness and that comes with more sensitivity to energy, higher dimensional influences, entities etc. Essentially a type of meditation induced clairvoyance allowing the sense of "things" nearby, good or bad, they can be equally scary if you dont know what you are sensing.
Now these astral "things" can do you no direct harm. They cause fear and influence you and at worst "leech" your personal higher dimensional energy which can physically cause fatigue, anxiety, fear, depression and illness (not saying all of these symptoms are caused by this, just saying these can by some of the causes in some specific cases) etc. but never real harm unless shit gets out of hand which is very rare for most people.
These "things" are not to be feared, simply managed. They are not demons are any of that shit most of the time, they are actually quite easy to explain and not something that cant be dealt with or should be feared or given power in this way.
To put things in real perspective: Genuine natural negative astral and higher dimensional entities which could be considered the real "demons" of old do not bother with average folks who are no threat to them at all, they only care about those already aware of all of these aspects, those already traveling the higher dimensions, the real "high adepts" and those consciously working against their negativity with real supernatural means and abilities. The real white "magicians" you and I or most normal folks will never hear about or ever be aware of because they dont work in the physical.
The stuff that affects the average person like you and me are very small and pathetic in comparison and dont deserve any respect and fear. I will explain:
To put it simply humans have the ability to direct higher dimensional energy with intent (purpose), concentration and visualization, since aspects of ourselves exist in these higher planes. A good saying as that "Where focus/attention goes, energy flows". And this is true more then we might want to believe.
We just don't know this consciously so when we focus on negative aspects, fears, etc, we program etheric energy towards that goal. Energy doesn't differentiate between i want or i dont want, it simply delivers what you think about or focus on. This is the real concept behind that very simplified manifestation stuff like that movie The Secret etc which tries to teach us about using this concept towards positive manifestation through energy manipulation.
We have the ability to "create" (meaning transform, manipulate, manifest beyond the accepted physical methods) but because this is unknown to most, most don't realise the effect of negative thoughts and how they create more negative occurrences in our lives. This is why patterns occur. Failures make you focus or fearful of failing again and therefore perpetuating this pattern through the "your wish is my command" effect, which goes way beyond the idea that negative thinking only influences our confidence or some other basic shit like that and thats how it creates patterns. There is way more to it then some simple physical or psychological effect caused by negative thinking.
Anyways, most negative influences or weird effects that happen are very likely to be artificial astral entities or imprinted energy (they have many more accurate names like thought forms, artificial entities, elementaries, god forms, tulpas etc) unconsciously created by yourself or other humans nearby and very often people who stayed in your house or vicinity earlier or many many years before you.
If you have issues of bad shit always occurring to you that dont manifest supernaturally but rather in your life physically, its usually a negative thought form you created yourself with constant worry, concentration and the accompanying visualization of the negative effects you are trying to avoid. Can eventually be resolved by changing focus to positive intent, ideas, visualizations etc which will overpower and dissolve the negative thought form.
If its definitively seemingly supernatural or seemingly unexplained and not normal that doesnt fit in with your thoughts or your own negativity about yourself, it may be basic negative energy or negative semi intelligent entities (depending on the level of concentration and emotion) unconsciously created by somebody else focused on intense negativity towards you (make any enemies recently?) and therefore unconsciously forming and directing energy towards you imprinted with negative intent, or less likely something remaining behind in your home from previous owners or any type of intense negativity in the area that might have created persisting astral influences.
Just to clarify, the astral is considered the emotional plane due to the spiritual law of analogies. What this means is that emotions effect the astral the most and provide the most "power" to the creation and manipulation of astral energy.
So the explain the above, when you focus on negative thoughts, or others do so towards your or in your area etc and most importantly its accompanied by strong or intense emotions of whatever kind, its very easy for these energies to be focused and formed/created in a way that can affect you or others, or anybody in an area where much negativity or intense emotion has occurred (fear, pain etc).
This is the cause behind hauntings, localized wierdness, bad feelings etc around certain places where past things may have occurred. Even people that give you weird feelings are likely emitting negative energy towards some kind negative intent that can be sensed by yourself to some degree if you where of a different positive "frequency".
I know this is hard to believe. I have seen a lot of this stuff astrally. Additionally I have received clearing and healing from a well respected and more advanced person who cleared multiple negative thought forms from myself (among a ton of other things that are just to crazy to mention) that I had created through my own fear and intense PTSD concentration as well as 6 negative artificial entities from my own home that had been causing other types of lesser influences that had been around before we arrived.
Just to point out that the major issues for most people are the energies created by themselves because the imprint on the energy is focused personally unlike shit left behind by somebody else. Negative entities created by somebody else are usually programmed to effect that individual or another person in their life and therefore might be sensed by other random people but would not necessarily be programed to influence them directly and have far less effect them self created shit. The point is most shit in our lives are created by ourselves unintentionally.
Lastly to not cause unnecessary fear, these are not easy to create and require intense constant and regular focus on the same idea or fearful comcept etc for a long period of time. This is not done fast or easy or with a few negative thoughts here and there.
Some people like the rare and real magicians/mystics/shamans can do this easily because they have trained their intent and imagination skills but for your average person these issues are caused by regular focus on a similar idea over a longer period of time, providing a trickle of power to the thought form over time. So its not necessary to be concerned by random negative thoughts, as long as they are squashed and dont become a habit.
Immediately afterwards all my anxiety PTSD fear and other anxiety that i know was not or no longer mental/physical or drug related completely vanished, plus i no longer saw them in astral or experienced fear/influence when astral traveling. I was shown how to do this and its so incredibly simple its ridiculous, simply done via your intent, which proved the point to me that these influences and entities exist by our will and ignorance about them alone and they can be dissolved back into the spiritual elements and astral material easily simply by asking and intending it to be done with some basic visualization skills.
I get fukin annoyed when i realise for one how much suffering and pain we inflict on ourselves unnecessarily in this way because we don't know better (not our fault) and secondly how much suffering we allow to remain around ourselves influencing us because we don't know how easy it is to remove it, how much power we have in this regard, and lastly how we give in to fear through ignorance instead of having the information and related confidence to fight back. I am guilty of all of these but glad to be finally learning the truth of the matter and learning how to take some control of my life back.
Knowlege is power, far more then we know.
Edit: On the Incubus/Succubus query. Most of the time these are also artificial and created in the same way as other astral thought forms, when its a mild effect. In this case it would be intense focus/concentration combined with sexual (emotional so there is the power) energy and visualizing some sort of physically representation of your fantasy over a longer period of time.
This can result in a specific type of partner, that might look the same or similar to previous partners or have similar traits to them that you might not want. Once again, creating a pattern in people your seem to fall for all the time could be influenced in this way.
When you are talking about real, powerful or natural non artificial Incubus/Succubus that seems to effect you supernaturally you might feel intense sexual attraction, desire, related effects randomly, especially when alone and its clear its not from your mind. It may have a sensation of being pleasurable but also unintended or some sort of violation. When it feels entirely inappropriate and not related to anybody you know or thats around you thats quite a good sign. But this is extremely rate and usually requires a magical evocation of a well know Succubus entity.
OP, your experience would not be related to this. A real Succubus experience would feel like the most amazing sexual experience you ever had, either consciously when awake experienced through touch and sensation or in the astral with all senses via a really vivid dream. It might be initially considered a positive experience however the reason why these Succubus exist is as a way to once again leech energy just like other negative astral entities, but by providing a seemingly nice experience sexually, it initiates acceptance in the victim and allows greater or longer access to their energy.
The result of this experience would be incredible fatigue, depression, anxiety etc or something resembling a bad hangover for the next day or days afterwards since you are low in etheric energy.
You do get many who purposely evoke Succubus type entities for the seemingly positive results who are happy to sacrifice energy for a few days but this is no good for anybody long term and is very short sighted especially for future spiritual growth and overall health and well being.
