Why does your body shake when your about to fall asleep?

Some believe this is because you are losing consciousness too fast, and so it is the body's way of moderating this. Others believe it is just because of stress, caffeine use, or strenuous activities during the day.

This is only problematic if it causes a cycle or causes anxiety about falling asleep. If you are startled awake because of the jerking, then you may become fatigued and worried about going asleep, thus increasing the chances this will happen, and increasing the sense of dread.

At any rate, this seems to be normal, and you should not worry about it. Just relax and continue trying to get to sleep.