Why does my ipad screen go dark randomly?

I have an iPad mini (5th generation) running IOS 15.5. I closed the cover on my iPad, which makes it go to sleep. When I opened the cover and tried to wake it up, it was completely black, and no swiping or tapping or button pushing would wake it up. Finally I took it into a room with no windows, closed the door and shut off the light, so the room was completely pitch black. I was able to see that the iPad was in fact on, although the screen was barely visible. Working in a pitch black room, I was able to log on and turn the screen brightness back up to regular levels. I have had this problem before. The screen randomly goes dark, and the only way to fix it is in Settings. Because the screen goes so dark, it's almost impossible to find Setting and set the brightness. I do have "TrueTone" on, but that shouldn't make the screen go completely black. Please note that the iPad is fully charged and normal temperature when this happens.

Any suggestions on how to prevent this extremely inconvenient and unexpected behavior?