I have no trouble falling asleep. However, I awaken at 2
or 3. Have two mugs of coffee with my Internet, collapse about 6.
Awaken again about 8. Nap 1 hour after a 1PM lunch. Drag myself to tasks.
Doctor says I need REM sleep, but adding my nap says, “Close enough”.
Falling asleep for a few hours, waking for a few hours, and then finishing sleep for a few hours is called biphasic sleep and may be perfectly natural for adults. There is little “science” on it, but many references in ancient literature to a first sleep and second sleep.
I’ve been experimenting with it by setting up peaceful but productive tasks before I go to bed so those waking hours are pleasant rather than laying there for 3 hours in despair because I can’t sleep! So far so good...I feel much better.
It isn’t the waking period itself that made me feel bad, it was the stress I put on myself over it!
A solid sleep block of 8 hours may be a 19th century habit, like eating 3 meals a day. IOW, not how people actually lived for most of human history.