Screen lights and stays on at night


I set my phone down for the night and screen goes black. Fine. BUT inevitably every night, regardless of screen timeout settings, I wake up and see the screen light is shining bright... There've been no calls or messages. It comes on for some reason and stays on.
I turn it over face down for all night. I get up in the wee hours there it is: on, shining bright no auto shutdown of screen light. It ignores it's own settings.
I check screen time settings and they're correct,... and it goes off fine during the day within 5 seconds and stays off until I click a button. But only at night it comes on, stays on. So now my body clock gets up to turn dumb screen off and hard to get back to sleep . I shouldn't have to turn it off every night and my job requires I keep it on 24/7.
What is going on and how can it be fixed?!