SOLVED! WDDM Service Not Running – Step-By-Step Tutorial
Quite a few factors, minor as well as significant, can mess up the operation of the WDDM service. At first, you should consider manually restarting WDDM and setting its Startup type to Automatic. In addition to that, it's a good idea to update drivers in Safe Mode, download and install Windows updates, ...
Feel free to take a look at our guide if you don't know how to implement the fixes by yourself.