I get the famous shakes sometimes while smoking.
I beleive it is simply caused by anxiety or possibly a small panic attack brought on by the weed.
Symptoms of a panic/anxiety attack are known to include SHAKING , fast heart rate, racing thoughts, paranoia, alternate body aches or pains, chest pain, dizzyness, feelings of dread, and rarely nausia. Sound familiar?
I have alot of experience with panic anxiety attacks while not on weed, so I can easily recognize them as such when I smoke.
While a bad panic/anxiety attack can make you feel like your dying (many people go to the hospital during a panic attack thinking they are having a heart attack) Nobody has ever died from a panic attack. Mine usually last for an hour or so but can last as long as an entire day.
Panic attacks feed off your thoughts and grow with your anxiety. For example if you start worrying about your heart rate, your heart will start beating even faster.
The best thing to do is to simply reassure yourself that it is simply anxiey. Remind yourself that is only temporary and cannot hurt you. Destract yourself from focusing on your body (or whatever your obsessing about). When I have a really bad panic attack I sometimes play tetris becuase it demands my concentration and destracts me from focusing too much on how bad I feel. Usually something mentally involing like this will help ease the anxiety.
Benzodiazapines can help with this anxiety, but i don't recommend them. I have gone through Benzo addiction/withdrawal twice now and the rebound anxiety from getting off the benzo's will make the pot anxiety seem like a warm dream in comparison.