Involuntary reboot and changes

I’m the use of a Lenovo ThinkCentre M93, and it is a dandy little all-in-one. Yesterday, on the other hand, I watched in amazement from around the room because the device rebooted itself for no obvious explanation why. When it got here again up, my run of the mill Windows 10 desktop have been changed via a bland grey display with just a handful of tiles for fundamental systems. The shortcuts I stored on my desktop have been long gone. I will nonetheless open systems, however I will handiest run them in complete display or minimized. I will not break up the display with two or extra systems. (*10*) of all, I will’t determine the best way to get it again to the pre-reboot setup. And much more worst of all, I will’t appear to seek out any beef up from Microsoft. Anyone???