Most propably a EROM issue as mentioned above.. Could also be battery doh.. Test your battery in friends mobile, test their in yours.. Charge in different available ways: Charger, Usb cable /doesnt charge full..+ slower\.. might as well try a desktop charger..
EROM could be caused by taking out the battery when cellphone is on..

Anything?
Try hooking it up with Setool/XS++ and post a log..

Have a nice day (: