iPhone turning on by itself at night

I have the same problem since one of the last updates. I turn the iPhone completely off before I go to sleep and in the morning it is running again without me doing anything. And no, it is not the turn display on when you lift your phone function. The entire system is turning on after a shutdown

I am also using same IOS on iPhone 15 plus. I force turn my phone off and it is suddenly turning itself back on without me even touching it. What is happening. It’s actually frightening me. Please help.

Probably you mean the display turns on.

Go to Settings > Focus > Sleep.

Configure Sleep Mode with your bedtime and wake-up time.

Sleep Mode will automatically enable Do Not Disturb and dim the lock screen during your sleeping hours.

Set up a Sleep Focus schedule in Health on iPhone