Same issue here. Had 8.1 for awhile now. Seemed to start doing this after the firmware update. Very random. Can be watching a video, working on an Excel spread sheet etc. Doesn't seem to be type cover related but could be. Again started with the latest firmware update.
Surface Pro 128 GB / Windows 8.1 / Touch cover
This is a problem that is not related atleast for the most part... to any particular program, or even extended video HD output. I used my surface pro 128 with NO crashes and almost no problems at all, I had never been more impressed with a PC in my life, and I work on them all the time, build them, and I'm very fond of windows 8.1. However, the surface pro certainly is not fond of 8.1, atleast from the update. As soon as I finally updated it, it wasnt on more than 5 minutes before it did its first shutdown. It got so bad I had to reinstall windows, and getting the office product key from microsoft was so easy and they were so helpful, that time. Now same problem, it was an occasional thing, now it gets warm, it says im using almost 100gb of HDD space, but I cleaned out personal files and many programs... including the .windows.old file from the last reset. Where is all that storage gone, and its become slow, extremely unstable, and I wont use it now because I dont want to damage it anymoe.... the random cut off even when cold, thats just not good for any PC/tablet, whatever.. I know its random because I tried many scenarios... the one that suprised me was that it rarely will crash when in remote control of another PC in my LAN.. im thinking i have no clue, its not a peripherial, idont think because it does it when im on it, it does it when its sitting running on low brightness, power saving mode on and cool... what do i need to do to fix this... ive taken apart laptops, more desktops than imaginable, but i really dont want to disect this thing.... Please Microsoft help me out here.. or anybody, im about to reset it back to windows 8 and take everything off it.... i don't like regular win8, but i like it better than not having a powerful little machine... Maybe i shouldnt ask this, but what about Linux maybe, or windows 7? im open for any help i can get... thank yall..
John Hawkins
admin/owner Webpcdesigns.com
**personal information removed**