Did you think of looking at battery usage and see what is using energy? Might be a good check, sometimes apps run a lot in the background and we swear we are not using themHave absolutely had this issue. I was shocked. I usually finished the day with about 50% left on my 12 mini. After updating, I've been getting down to 0% with the same use! My poor mini, it already struggles enough with battery life lol
EDIT: I also experienced the unexpected heating issue while doing basic tasks like looking at email.