Thank you for this info. I did this for years, often waking in the middle of the night, usually between 2 and 4, and unable to go back to sleep. So, I started doing things like reading, or watching a quiet movie, until I felt sleepy again, usually around 5 (or 7, if I didn’t need to get up early).

It wasn’t until many years later that a friend mentioned to me that what I was doing was called “second sleep”, which I’d never even heard of. Now I try to plan for it, especially on the weekends.