Since I upgraded my iPhone to iOS 7, I suffer from random crashes/resets, where my iPhone reboots and enters a reboot loop (Apple logo, black screen, reboot, Apple logo, black screen, reboot, etc) that I can only exit by restoring the device (resetting doesn't help).
Some more information
a) The device: iPhone 4, 32 GB, has never been jailbroken, and has never shown any similar issues before.
b) The crashes/reboots: I haven't been able yet to find a pattern when and why they happen. I had reboots when searching for an app, when pluging in the wall charger, when entering the access code, and even when doing nothing at all (iPhone in my pocket). The only constant is the reboot loop after the crash.
c) What I tried so far: I restored the device several times, using normal restore (with the iTunes logo) and DFU mode (black screen). After that, I recovered from a recent backup (takes some hours), and everything is ok again - for some hours, until the next crash and reboot loop. I also set up the device as a new phone, and there it seems stable, so I exclude a hardware issue. I tried quite a few of the advices that I found when googling for reboot loops: reset all settings (this led to an another immediate crash and reboot loop), disable app background refresh, etc.
I've been using this device for my daily business. With the current instability (and the couple of hours it takes to bring it back to life again), it became more or less useless. I wish I could downgrade again (I know that I can't). My assumption is that either iOS 7, or some incompatible app or some corrupt setting is causing this situation. But I don't know how to proceed to isolate and eliminate the issue. I really would like to avoid setting up everything from scratch again.
Any advice is greatly appreciated!