Problems with my iphone turning off

If it doesn't fix itself with the reset, then try a restore (make sure you are synced up).

If the Restore doesn't work, then a return to the Apple or ATT store is in order.

It wouldn't explain why you can't turn it back on but there is a setting that determines whether or not your phone ever turns off or auto-locks automatically. Go to Settings, General, auto-lock. You can pick 1,2,3,4,5 minutes or never as your setting for whether or not your phone will turn off or sleep automatically.

I don't mean to be elementary but since you asked about "settings" I wanted to make sure you were aware of that one.

I have the same issue with my new iPhone(exchange from my old iphone). I never had this problem before with my old iphone (low speaker volume). I received new iPhone 2 weeks ago as warranty exchange, and about once every 4-5 days its turns off by itself with battery being around 50-60%, for the first time I could not turn its on the regular way , brought it home connected to the charger and its came on. Second time I was able to turn it on by holding home and top for about 10 sec with apple logo comming up, when it came on my charge was about 40%. On top of all I missed so many important calls and first time arround was in Airport and could not call my wife to let her know that everything is ok 😟

I bought my iPhone 3 days ago and yesterday it turned itself off and on about 12 times...give or take. So last night I did a restore and charged it from about 20% to 100%. This morning I have had it happen twice already. I made an appointment at the genius bar at my local apple store to get a new one. Has anyone had this crazy frequency of their iPhone turning off and on so much?