system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do we sometimes wake up in the middle of the night and close our eyes or sleep for what feels like 2 minutes, but when we wake up a couple of hours have already passed?

It used to happen to me when I was young. I'd wake up around 2 am then close my eyes on what feels like a 2 minute sleep or nap. Then i'd open my eyes, and see that it's past 6 am.

What makes this happen? Most nights are not like this. It felt like i was time traveling.
gpt
You feel the rate of time by the amount of thoughts/your memory of your own recent thought processes. Your brain just assumes you think at a constant rate and you use that to measure what seconds, minutes, and hours feel like.

But you don't think at a constant rate.

This is why time can fly by while you are "in the zone" (muscle memory actions without thinking about them), and why it goes by super slowly when you are anticipating something (constantly thinking about time)

So, when you are in non-REM sleep, you aren't remembering your own thoughts at all, so when you wake up, you feel that no time has passed.