I was using my phone at usual and it suddenly made a weird buzzing/grinding noise and the phone vibrated. I turned the phone off and took it out of the case I have for it. The back, specifically up by the camera seemed uncharacteristically hot. I believe the CPU is up there and I hope that this doesn't mean that it is going. The app I had open when this occurred was Snapchat, but I wasn't on the camera at all. This has happened before with the phone just sitting on the home screen.