Samsung Galaxy S1 Constant Reboot Cycle I left my Samsung Galaxy S1 charging overnight plugged into my computer (as I usually do) and when I came to use it in the morning, it was turned off (to my surprise).
When I turned it on, it goes into a constant reboot cycle, where it turns on, gets to the home screen and then about half a minute after, just reboots itself again.

I am able to get into recovery mode and download mode and I can keep it stable in safe mode - but have limited access to apps.
My questions are:

(a) does anyone know what would have caused this?
(b) what can I do to stop it?! without the obvious factory reset?
(c) I originally thought it was a battery problem but now that I can sustain it in recovery and safe mode, am I right in saying that the battery is fine and its most probably a software or app malfunction?
Does your sdcard have multiple partitions?

Most recoveries have built-in repair function to scan corruptions in sdcards which prevents your phone from booting properly, it is under Mount -> Repair if you are using CWM.

If it did not help, try removing your sdcard temporarily to check if it boots up properly. If it successfully boots then you need to reformat your sdcard, make sure to backup first.