Could be a billion things...Irrelevant.
All I know is do not make this a habit. If you feel you have sleep problems see a doctor and get them to refer you to a counselor and they can help you out and try things like CBT which i've just explored and it's very useful for any sleep related anxiety.
My insomnia got so bad that it lead to RC 'legal high' benzo use (and some opiate use that wasn't addiction but became problematic) - I thought I could control it, like most people believe. "just once or twice a week maximum, or for the odd stressful situation". That's fine, if you can manage that, but you are dancing with the devil: Benzos trick your mind the same way opiates do (but worse in my opinion, with infinitely worse WD's than heroin). Suddenly it becomes 3 times a week, 4 times. Then you believe you can stop. You might be able to the first 4 or 5 times with only rebound symptoms.....But it's so very easy to have a "fuck it" moment and use it for a whole week, or every other day for a few weeks, thinking you can stop because they seem pretty benign... But then you try to stop and realise you are in a world of shit.
Sorry not preaching, just dont want another benzo horror story and a potential year (or years) of misery for you (or anyone). I have been tapering for 9 months now with a few relapses with diazepam after fucking with clonazolam,flunitrazepam, etizolam, etc.and I am now having to get CBT therapy at a clinic because I literately cannot function without popping a benzo at night: My brain and mind has literately forgotten how to sleep naturally and now it's going to take a year and a huge amount of effort and suffering to get it back. Not worth it. I was stupid and arrogant thinking that just because I could control other very addictive drugs like meth, oxy, even heroin (chipping) for the most part relatively well, I could control benzos. Nope. For me they are the most addictive drugs in the world.
Be very very careful. If you must, take it once a week: I get they can be useful for pre-op anxiety, phobias of flying etc and very short term use under strict supervision (seriously, see a doctor, don't self-medicate with benzos). If you find yourself taking more than 2 a week stop immediately and consider why you need to use them.