In the past, it was simply waking up, this last time it was definitively shut down.
Yes- When you 'restart' or 'shut down' and reboot, does it seem to perform this normally?
I have only removed the "Tablet" once, so I can't answer that question.- Does your Surface Book shut down when in Tablet mode, normal mode, or both?
I doubt it. I keep in on my desk 99% of the time. I do have it connected to a Docking station with an external monitor, speakers, USB Hub and a couple SSD.- Is there a chance some metal shavings, debris, or pieces of a vinyl cover, etc. are fouling a connector port?