Now it has shut itself off and will not turn back on
First thing I would try is a new battery. If it comes back on and it doesn't reboot itself then the problem is the battery. If the problem of rebooting itself persists, then reboot the phone in safe mode to see if the problem goes away. If it does go away, then you probably have some app that is in conflict with your operating system.
Craig.Gill,Let's fix this! I know you need your phone. Have you tried removing/inserting the battery? If so, try completing an alternate factory reset here http://vz.to/1r32MPE (this will erase everything) and test. Please share. TominqueBo_VZWFollow us on Twitter @VZWSupport