Received my Nexus 6P two days ago. Today, with no warning, and with a full charge, the screen went black. It would not reboot. Eventually I pushed the start button and the down volume button, and after a few seconds the little Android guy appeared, and after a few more seconds the screen indicated that my apps were being optimized. It thereafter booted up. Since the app optimization occurs after a software update (I've already had three of them in two days!), I assume that something happened during an update, but it was somewhat disturbing, as I have never had this happen with a phone. Anybody experienced this, or know what was happening?? Thanks.