Ok to explain, today my phone got the latest software update. Not thinking I just installed it because of course I would, its an update.
But since then, tapping a notification, opening messages and even being in system too long will cause the phone, an S20, to black screen then return to the lock screen.
I can't find anything online on how to resolve this, as other crashes/restarts are based around apps, not the notifications on both the lock screen and swiping down, the text message app or system itself (either the access in apps or from the cog on swiping down). Can anyone help me? This phone cost a lot and I can't afford to just replace it in the current circumstances.
I tried to do this as you suggested to no success, I cannot even get to step two as the phone just continues to start back up regardless of button input.
I was able to access the settings and clearing the cache but the problem persists, notifications, text messages and systems continue to cause a black screen and return me to the lock screen.
I rebooted in safe mode and could access everything I couldn't before. I'm not sure what happened but I deleted free wallpapers and icon themes I downloaded, and returned out of safe mode, and the problem is now gone. Now I'm not sure how I'll get new wallpapers if that is the problem, or perhaps it was the icon theme as the UI is different in this update.