Hi All, I have an iPhone 4 (32GB with 2-3GB free space). I have had it for a long time and never had any problems. I upgraded to IOS 7.1 yesterday and things seemed ok. 24 hours later and it keeps crashing. It keeps rebooting and showing a black screen with the apple symbol. It will do that for about 15 minutes on and off, then go to the home screen for about 5 seconds then go back to the black screen with apple symbol. It was working for about 5 minutes and then crashed again and the cycle continues.. What could it be and what should I do?