I personally have an iPhone 14, and I woke to a black screen but the phone itself still vibrated. Tapping around, I could figure that it was on and was responding to my taps; for example, I could tell I was at my locked home page when I felt the phone vibrate in response to, what must have been, me attempting to enter a password. So, I powered off the iPhone by holding down the power button and the upper-volume button, then swiped right at the top of the screen just as I would normally, even though I couldn't actually see anything. I could tell my phone powered off bc there were no more vibrations. Then, I powered it back on holding both the power and the increased volume. It eventually showed the apple logo and brought my phone's display back. So odd.