To be honest I thought I was either going mad or just not clicking "shut down" accurately enough or something 
 
But no, I just confirmed it...sometimes I will click "shut down" and Windows 8.1 will reboot instead. Anyone else experienced this frankly bizarre problem? 

I haven't experienced that but Sunday I moved the mouse to activate the screen and I was at the login prompt. All applications had been shut down and Windows did a self reboot and it wasn't some Windows Update thing, this was in the middle of the day, I had only taken a lunch break. Really bizarre.
 
Regards,

That doesn't sound good at all.

If your Windows is set to reboot on an error, and there is an error during the shut down process this could happen.
The easiest way to test this is to turn off the automatic restart on error in the advanced system properties. Automatic restart is really designed to keep an unattended machine running in case of an error.
 
http://h10025.www1.hp.com/ewfrf/wc/document?docname=c03413399&cc=us&dlc=en&lc=en
 

Thanks slartabartfast! If there's any error happening during the shut down process then I have a feeling it's Google Drive related. 

It's what we like to call a "feature." 

my win xp never does that.
 
:)

I had Windows 8 shut down on me a  couple of days ago when I was working in SONAR ( running the plugin utility )
didn't know what happened , and when my computer restarted all I got was a black screen …no mouse no nothing 
freaked me out ..to tell you the truth , I wasn't happy about it ...
eventually after repeated attempts my computer booted ...
I'm not cool with it ….
 
Kenny