A part of my phone is overheating

The red circle shows where it heats up the most but overall the black circle shows that’s the area that heats up. It heats up almost immediately after I turn on the phone and then it would force shut down and start a boot loop. Idk if that area is the motherboard or the logic board. If possible id like to know if it’s possible to fix it or at least identify the problem. I’m already thinking of getting a replacement battery, but idk if it would help yet.