As recommended by Samuel Pepys between first sleep and second sleep.
There is lots of research, suggesting that split sleep in the human norm:
https://www.sciencealert.com/humans-used-to-sleep-in-two-shifts-maybe-we-should-again
https://www.bbc.co.uk/news/magazine-16964783
https://www.history.vt.edu/Ekirch/sleepcommentary.html
So, the message is, chill. Don't stress about a normal pattern. Relax, let the mind drift.
I follow a technique from headspace - Take a few deep breaths, relax and run gently through, in time sequence, the events of the past day, not in detail, just the headlines, if other thoughts intrude nudge yourself back to the events list. When you get up to date breathe steadily and start counting breaths 1000, 999, 998..
I very rarely get to the counting stage.
The thing that used to stop me drifting off again was repetitive thinking : I must get back to sleep I must get back to sleep I must get back to sleep... It's a bit like not thinking a bout purple elephants
.