I had my phone which is HTC One M7 for a while (around 2.5 years) and it suddenly startet to reboot it self. It was an endless cycle right until the battery was drained. The phone would boot up until HTC logo showed up and then turned off and started all over again. It seemed like the power button was constantly pressed on. I've read somewhere that my power button could have short circuit and that it's a hardware problem which is more likely since I haven't rooted my phone. I tried to get into the recovery mode by holding volume down button only and it worked every time. When the recovery mode menu showed up phone rebooted quickly and I couldn't do anything. So, I want to fix this problem since I like my phone but I don't know which part I should be changing. Is it just a power button or the whole upper board itstelf or maybe something else???