I have an iPhone (3GS) that does not have cell service (I mainly use it for wifi and iTunes) When I updated the iPhone to the new iOS 6, the thing now won't even turn on! It powers up to the Apple screen, then shuts itself off. Then it powers up again to the Apple screen and then shuts itself off. It does this until I take it off the charger and dies from a dead battery. Has anyone experienced this or know how to fix this issue?