Stage 1 non-REM sleep is the changeover from wakefulness to sleep. During this short period (lasting several minutes) of relatively light sleep, your heartbeat, breathing, and eye movements slow, and your muscles relax with occasional twitches. Your brain waves begin to slow from their daytime wakefulness patterns.
The body isn't completely relaxed. The body and brain activities start to slow, with times when the body briefly [twitches]. There are light changes in the brain.
