Overheating

It is not clear here in your post about the ambient temperature in your area where you are using the iPhone. However --> Keeping iPhone, iPad, and iPod touch within acceptable ...

Store the device where the temperature is between -20º and 45º C (-4º to 113º F). Don’t leave the device in your car, because temperatures in parked cars can exceed this range.

Use iOS devices where the ambient temperature is between 0º and 35º C (32º to 95º F). Low- or high-temperature conditions might cause the device to change its behaviour to regulate its temperature. Using an iOS device in very cold conditions outside of its operating range might temporarily shorten battery life and could cause the device to turn off. Battery life will return to normal when you bring the device back to higher ambient temperatures. Using an iOS device in very hot conditions can permanently shorten battery life.

Yes I have been having a problem since I bought it. They actually sent me a new one and it does the same thing. I don’t have a regular computer so I do all my games and everything on my phone. When it gets really hot the screen actually gets really dark also. If I turn my phone on I play Pokémon go and I try to walk around the block to get some exercise and the phone turns dark and it overheats in less than five minutes it’s ridiculous I don’t understand. They should either do a recall and give us all new phone or something.