I had that today in class and it was weird.
It's happend to me before, but not while in class, aha. I cant fall asleep in class, but I remember being in the hospital when I was nine or ten and I was falling asleep on one of the beds and that happend to me, the whole bed shook and my dad just looked at me, like cut the sh!t and quit messing around. :D
Yes :| Like it feels like youre falling? It is known as a hypnagogic myoclonic twitch or “Hypnic jerk”.
Haha that happened to me, I had to act it out that something stabbed me so I jumped ha.
lol yes it's embarassing if someone saw it when it happened though! haha