I have read about first and second sleep as well, BetterNow.
Part of it was, I think, that people went to bed when it got dark, slept for a while, woke, stayed up, then went back down.
I hear you. As I have aged, sleep proves problematical at times.
But, don't want to take anything beyond the OTC stuff, and not much of that.
Fortunately, I am no longer working.
I can usually nap in the afternoon if I have had a bad night.
Slept incredibly well when I was younger.
Sigh.