Hello everyone. I had the exactly same issue with my Pro 10.5. It also had been reported for other devices and in other forums.
This is not a simple software issue.
Bought my Pro in January 2020 (still sealed). It was fine until March. Then there had been a single, but major crash/freeze, probably the moment when the damaged hardware component failed for the first time. As soon I somehow managed to reset it after some minutes, the massive heat issue began. How you can confirm it:
- Lower left area next to homebutton heats up after 4-5min whenever the display is on. Brightness doesn't play a major influence and as you turn the display off (background activity like music/radio can continue), it will cool down again.
- Dramatic battery drain, like if the defective component/chip drains Amperes like crazy. You can really watch 1-2% dropping every 3mins, even in absolute idle
- Neither a soft nor hard reset, nor software update does solve the issue
Only solution: If you still have warranty, use it! Dont waste your time like me with the lousy telephone or chat 'support', hell, even the pick-up service was pathetic, as they just sent it back to me a week later later with "no issues noticed". Guess what, still got hot. Either go to your local Apple Store or Gravis (like I did) and demonstrate the issue. Reset you device before doing that so they see it even runs hot after a few minutes in the 'welcome / select your country' screen. It is crucial that a staff member or supervisor sees and confirms the symptoms.
--> About three days later, I could pick up a new / refurbished unit (0 cycle counts) from my Gravis which is fine again. No heat, good battery. I strongly assume a defective display controller chip. Don't ask me how that happens, as I handle my devices very gently. Good luck everyone!