system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:When I am starting to fall asleep, why does my body sometimes jump or jolt me awake?
gpt
It's called a Myoclonic Jerk... It is basically the brain sending signals to your extremities to ensure they are still there and working.  When falling asleep, the brain tends to "lose contact" with arms, legs, even organs.  It may be a sign of mental illness, but in most people is perfectly normal.