My iPhone 5 will just shutdown on occasion and then will not turn back on. It says there is no battery life left. This is not true because it has around 30% left. I just plug it in for a few seconds and it boots back up with the battery percentage it had before it died. It does not do this often, and only a few times since I have had it since November. Does anyone know if this is a battery issue or a software issue, and is it a big deal or something not to worry about. Other than that the phone works Great. Sean.