I have been having the same issue with my iPhone 12 Pro for awhile now. In addition to the screen freezing, unable to open any apps or restart the phone, I cant even swipe up The app just get stuck in the middle of the screen instead of closing when swiped to close. Apple has been very unhelpful. I have had to rest my phone to factory settings a couple of time. When i had the beta ios, i kept reporting the issue to via the feedback assistant because the support team could resolve the issue and never got any response back. I was actually at the apply store today and the same old fix of resetting to factory setting was done but the issue occurred not long after that . Complete waste of my time. It is getting extremely frustrating to use the phone. Very disappointed to say the least.