iPhone 12 mini freeze after I go out

A week after I bought the iphone, I took it to go out. We use motorcycle and put my iphone on my backpack. Once we stop by at the nursery and talk with the owner. I took out the phone and open camera to take two pictures. When I try to take the third picture it's freeze, just stop working. The phone is hot. At home I restart and back to normal.

Three weeks later I go out again and bring the phone, when home it's freeze again. I can't swipe and open the phone. Using SIRI to open and it's open the address book. I start to click the home. After a few second it's back normal.

What happen with my phone? Is the mini easyly get hot when you carry around in your purse? Should I put the phone in the pocket? What is the best way to keep iPhone when you go out?