My phone's (a Rumor Reflex) battery died, so I plugged it into a portable charger I have because why would you not charge your phone? But when I plugged it in, rather than doing the standard Rumor Reflex startup screen and then going to the charging screen, it kept doing the startup screen over and over. So I tried unplugging it from the charger. It kept going with the startup screen. I plugged it into a regular wall charger. It kept going. I took out the battery and put it back in several times. Each time I put the battery back in and turned it on or plugged it in, it would just keep doing the startup screen over and over and over, and I don't know how to fix this. D:
The best suggestion I can think of is, if you have a memory card installed, to remove it and attempt rebooting the phone then. Otherwise, based on my googles, this isn't an uncommon issue with the phone and it seems the best course of action is to take it to your nearest Sprint store and have them replace it for you.
This exact same thing happened with my phone. I couldn't get past the start-up screen. In the end, it was a software update issue that was causing the problem. Honestly, there's nothing you can do but send it back to your network provider for repair, since you can't even get it started properly to factory reset it.
