If it's a front window, the switch may be suspect. Sometimes you can take them apart and clean the points. Be careful not to loose the various springs and ball bearings. New switches are about $20. A rear window problem might be caused by the cord being broken. Sales people's cars, especially the rear driver's side door, typically need the cord replaced. Mine does. I have trouble with my electric seats. I took a seat switch apart. Not recommended. I had springs and ball bearings all over the place. New switch fixed the immediate problem but pointed to a wire harness problem which I have yet to tackle.