[Hash Brown]

I tried restarting the phone, doing a complete factory reset, uninstalling new apps, letting it cool down just in case it had overheated, clearing the cache on the camera app etc. but nothing has worked. Every time I open the camera app, I wait a few seconds then the whole phone just turns off. Nothing like this ever happens with other apps and the phone is very new so I don't know why it is doing this.

[B. Diddy]

I would try booting into Safe Mode. If the problem persists, then it's probably a hardware problem. If the problem gets better, then something you installed it the culprit.

HTC One X Plus – How to reboot into safe mode | Phone Tips and Tricks

[wizzrah]

Hello.

Try doing a factory reset of the device. Is the device rooted or is it stock?

Sent from my nifty 2 year old AT&T HTC One XL