Your phone could be getting to hot for a number of reasons. The first one being over use. Having to many applications running on your phone at one time can cause it to overheat. Go into your task manager on your phone and stop all of the applications and just let it rest. The second thing would be to turn your phone off. The phone is overheating because of the battery. Therefore, if your battery turns off for a little, it gives the phone time to cool down to a normal temperature. With this HTC, the battery can not be pulled out to let cool so putting the whole phone in a cool area for a little time is the best way to cool it down fast.