Although I haven’t seen the issue on my Pixelbook, I saw some folks on forums and social media saying their device was randomly rebooting every few minutes. The good news is that Google has fixed the Pixelbook reboot issue with a minor update to version 65 of the Stable Channel, as noted by Android Police.
Details on what was causing the reboots haven’t been released but my gut says it had to do with Bluetooth. I say that because some folks were disabling the Bluetooth radio on their Pixelbook and, in some cases, the rebooting behavior stopped. Also, I have never had Bluetooth enabled on my Pixelbook and I never experienced the problem. That’s conjecture on my part of course, but it’s a reasonable one based on observation.
Regardless, if you have a Pixelbook, I’d make sure you’re up to date on the Stable Channel, which is currently at version 65.0.3325.209. Note that although this version has the fix, you can verify it by also checking the Platform version installed on your device. Type chrome://version in your browser and you’ll see two different versions: One for Google Chrome and one for the Version of Chrome OS: If the latter shows as 10323.67.5, then your Chrome OS platform has the fix.