Just experienced sponstaneous reboot with inability to complete restart Nexus 5x device. Was enrolled in Andoid Beta program. Unsure if had just received OTA update overnight. Phone was well charged & now unable to boot. Hard/Soft resets not functional. Talked to Nexus support and after walking through troubleshooting with them, will honor warranty. Replacement in the mail at no cost. Purchased the phone through Google Fi.
Just wanted to let people know, will update with more information as new device arrives.