iPhone XS overheating

Hi I’ve been on the phone to Apple this evening about my phone which is overheating. I have performed a complete factory reset and have an appointment at an Apple repair store on Saturday. Phone has never been dropped or water split on it, it was overheating in a a/c room and got so hot it was too hot to hold the phone, phone switched itself off no messages about overheating. Phone still under warranty.

Help.