system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do some people toss and turn while sleeping, while others will stay relatively still?
gpt
When you dream, many things happen! First thing to happen is that your mind runs subconscious 'checks' to see if you're actually out (sends twitches down limbs and stuff). When your body stops responding, your brain begins the process of entering sleep paralysis to keep you from acting out the dreams you are experiencing. A lack of this ability makes people sleep-walk, or to a lesser degree, toss and turn. It may also be that the fitful sleeper isn't experiencing true REM sleep, and as such not sleeping as deeply as someone who is still.