Nexus 6P constant power cycle and "no command"

Out of nowhere today my 6P looked like it was rebooting. I didn't think anything of it at first but then noticed it just kept cycling the 'Google' screen and getting no further. I held the power and volume keys to try and get it going, but couldn't boot it into any mode whatsoever. It either kept cycling the Google screen or, on occasion, gave me a "no command" error. I eventually got it to reboot itself and thought I might do a factory reset just to play it safe. I got an encryption error when it was starting up on a fresh setup, but it seemed to come back up in the end. Now, in the middle of reinstalling app backups it's started 'Google' cycling again and I can't get it to do a thing. Never had an issue with it, and not sure what I should do next (as there's not much one can do with these devices).

Has anyone come across and resolved anything similar?

Many thanks in advance.