I had the same problem with a rear electric window on my old Mk3 16v.
I didn't realise it didn't work at all when I bought the car, when I realised the fault I got the garage to "fix" it. Then every so often the window would wind down of it's own accord.
Took it back to the garage who told me that the window motor had been disconnected before, so their "fix" was to reconnect it. So the fault had existed before but the previous owner had disconnected the motor instead of trying to fix it. I got them to disconnect it again as I wasn't bothered about the rear windows and I sold the car a few months later anyway.
So I haven't got a good solution to that problem, but if you're not bothered about windows (
) then you could just disconnect them.
It might be related to a knackered door wiring loom or a dodgy switch.
You could try replacing the switch first. Also open the door and pull back the black rubber boot that covers the wiring loom between the car body and door. See if any of the wires look broken.
