iPhone black screen. non-responsive

[JM]

If your phone is completely black and unresponsive in the morning (like mine was today), try quickly pressing volume up, then volume down, then holding power button to force a restart.

That turned it back on.

FYI.

If your iPhone won't turn on or is frozen - Apple Support

If your iPhone has a frozen screen or becomes stuck, learn what to do.

support.apple.com

 

[High Desert]

Been there fine that on my 12. No idea what caused it to blackout.

 

[Mark359]

I have had this twice in last few weeks. Not just screen not responding but whole phone is dead overnight (visible form looking at battery usage). More than just annoying as alarms set for morning do not go off. Phone going to Apple for inspection