For a while my computer would power down and then immediately power back up, over and over again. The issue is that computers are always sleeping with one eye open, so to speak, and there are any number of things that can trigger a power-up. In my case, I disabled wake-on-LAN, and it solved my problem.
…Aaaand my system failed to suspend last night. I did the “powercfg -requests” thing, and it reported that Firefox was busy playing audio. It wasn’t. I restarted the browser and the operation went away. 
But was there a tab open that could have played audio or video? Restarting Firefox would close that.
Also, have you done any malware and adware scans?
Update:
Windows tricked me into upgrading to Win 11 (“we have important updates!”) and I can report after 6 weeks that Windows no longer has insomnia. Sleeps every time. Sweet.
I still hate Win 11. It’s buggy. The calendar and sound level in the task bar just stop working randomly. But I’ve found workarounds, at least for the sound level. I’ll pick up my phone to see the calendar when that breaks. Dammit. And they moved other settings to new places for no obvious reason. Dammit. And the Start menu shows me MS apps I never use until I click “All” to get to the list of my apps. Dammit.
In fact, on many Windows laptops, hibernation is so deep that nothing can disturb it. Including, say, hitting keys, or even the power button.
Yeah, I don’t use hibernation for that reason. It’s a crap shoot if it’ll ever come back.