Intermittent electrical failures can be frustrating to find. You can either wait for it to fail outright, then it's easier to find by tracing the lack of power from the motor circuit back with a multimeter; or check all wiring now for a loose or bad connection or an intermittent switch. It's less likely to be the motor itself if that runs normally (when it does run).
There is a Driver Door Module (DDM) inside the door that controls all the window functions, so start there, and check all wiring connections coming & going from that. Also be careful taking the door panel off - it uses push-in clips & you don't want to damage the panel (there is a special tool to take the clips out, but you can do it with 2 small screwdrivers if you are careful).
Getting a Factory Service Manual (FSM) either from eBay or Helm will pay for itself if you intend to do any work on your car.