I have an iPhone X that has suddenly been overheating. I have done a factory reset and when I start setting it up and have it restore from my iCloud backup it gets extremely hot. I have an iPhone xs max that I have tried out and it does not do the same. Could it be a hardware issue? Not sure if related but just the other day the iPhone X suddenly turned off and went to the apple logo "reboot" screen and also got very hot to the touch. I was at work and was not able to do much except try to power cycle the phone but when I did that it would go back to the same screen. It ended up running out of battery since it kept trying to reboot.