For as long as I can remember I've been experiencing the following: As I'm drifting off to sleep, or possibly just fallen asllep, I get a total body jerk. It wakes me up suddenly and it's visible to anyone around me. It usually startles my wife pretty good and wakes her out of her sleep most of the time. However, recently this has been happening when I'm wide awake, not falling asleep. I may be in deep thought, or no thought, but I'm always laying still, or sitting up still when this occurs. The jolts have gotten more violent and many times it actually causes pain (I suffer from chronic pain from my back, legs, arms, etc.). Does anyone have this happening to them, or have any possible explanations? Thank you.