I don't even know what to call it. Last night I had just fallen asleep when all of a sudden my entire body - or it felt like it - had a huge jerk. It was so powerful that my heart started beating 100 miles an hour (flight or fight). I've had restless leg syndrome...but this was nothing like that. Should I be concerned?
Sometimes when I go into a deep sleep...all of a sudden I jump and wake up...maybe a dream...nightmare, etc., but never felt concerned about it...thought it happened to everyone once in awhile...not sure what to say Amy... ~ Thoughts out to you ~ Colleen
Ok - thanks Colleen...probably nothing. This whole process just makes you so paranoid about everything - neurologically related! LOL
http://www.livescience.com/39225-why-people-twitch-falling-asleep.html
This should help you understand. =). Surely nothing to worry about, just don’t fall asleep in any trees! Haha!
LOLOL!!
Amen to that…i smiled and my eye turned… Lord what now…
Happens to me frequently as I am falling asleep - like literally falling! Apparently it is very common! 
It's a hypnagogic jerk.
http://en.wikipedia.org/wiki/Hypnic_jerk
It is common and normal. Nothing to worry about.
Judith