Why will my windows in my 94 Audi 90 Quattro only roll up every now and then?

When I bought this car it wasn't driven for about 3 months. The windows worked fine when I got it. When I turned it over and drove it the windows wouldn't go down for a little while and the stereo would not turn on. After a little bit they both started working and they work great once they start. When I turn the car back on sometimes they work right away but sometimes it takes a few minutes for them to work. Could this mean there is an ungrounded wire somewhere? Also, If so, how would one go about finding the problematic wire? Any advice would be greatly appreciated!