My dad has a 4S and I have a 5 and we keep having issues on iOS 7 with trying to wake our phones back up and they are unresponsivejust a black screen. Rebooting fixes the issue for a few days and then it will do it again. I think it's been happening more often with my dad, and he also has an issue where his phone will randomly reboot or respring (can't tell by his description). Apparently he was in the gas station and went back to his car and his iPhone was in the middle of rebooting with the Apple logo. It's pretty weird because he wasn't even using it before. He wanted me to ask on my "Apple Forums" if anyone else has had this problem?