It’s entirely possible that those brief shut-downs are due to updates being pushed out. They happen whenever the GF team gets one ready, but if you leave your machine off most of the time, you can get a little backlog that have to process before the startup calibration will run.
We’ve tracked down the bug responsible. While we don’t have a fix available now, the behavior is harmless, and doesn’t affect any other aspect of your machine or its operation.
I’m going to close this topic. Please post a new one if you have any other questions.