So my phone was dead, I plugged it in, and now it's behaving strangely. When I plug it in, the battery goes really fast from 0% to 5%, then twitches up and down around the 5% area, and then shoots up to 100%, but then won't turn on. When I unplug it, it dies. I guess it's a battery problem, but I don't know how this happened. It was working fine before. Any tips/insights other than to get a new battery?