Christine has an HTC One and now it's just rebooting. Leo says it can happen with any phone. It generally means something with the phone's data storage. It's called a "boot loop." She can go into recovery mode and start over, but that may not work. She could also try and root it with different firmware or a third party recovery tool. Clockwork Mod works well. Leo says she should first try going to her local store and get the expert to try and clear it.