So every now and then the phone will just get warm, not hot but a "would be nice to warm your hands on a cool day" warm. Occasionally it does this while charging and it also appears it doesn't charge when it does that either. The solution has been to stick it in the freezer or AC vent and that will knock it out of its funk, otherwise it will stay warm and drain the battery rather quickly.
Then on other occasions I'll check it, it'll be at say, 90, then 20 minutes later, I'll check it again and it's at 70.
Any ideas? Is my battery shot? Time to look at battery cases or replacing the battery?