I had been watching game of thrones on the Xfinity Go app and then locked my phone. Then, when I went to unlock my phone a little later and plug it into my computer (the exact order in which I did it I don't remember, as it was pretty much simultaneous). When I did these things, my phone began buzzing in a high pitch sound and the screen froze up. I'm not sure if it was related, but as soon as I hit the home button to close the app, my device restarted.
Samsung Galaxy S7