Gah...Had one in the middle of Statistics this afternoon. I managed to pass it off as something stabbing me in the back, but still embarrassing nonetheless. Somehow I knew it was going to happen because I was trying for the life of me not to fall asleep in class... -___-
This happened to a friend of mine in english one day! He was sitting at his table, dozing off, and then flails around like a madman with this absolutely panicked look on his face! It was pretty funny...
But more to the point; yes, I've experienced hypnic jerk many times before (a couple times in class ), but it usually happens if I'm falling asleep reading or studying in bed or on the sofa...