Are you using the keyboard case and closing it? On mine doing that eventually wreaks havoc with the touchscreen and causes a shutdown or other issues.
Also Windows 8.1 on my device was really buggy, it would constantly crash and there were other errors. I installed Windows 10 (lot of hassle sorting out drivers) and now it’s more reliable but will still sometimes turn off or crash due to poor quality drivers.
Just had a quick look in Event Viewer and the majority of unplanned shutdowns on my Vi10 Pro are caused by runtimebroker.exe (part of Windows App system).