I have a problem with the windscreen wipers on my A4. Occasionally they run slow, getting slower each day until they just about stop altogether. only a flick of the switch will make them go again, sometimes stopping in the middle of the screen. Then another day they will work perfectly!!

As they have worked perfectly for over a week I suspect the motor is ok.
Could it be a duff relay perhaps?

 

Don't guess that can be expensive unless you just want a whole new system. Going to be one of the 3 switch,relay,motor. Prolly either dirty contact in the relay or wiper motor brushes. But first check the connections you have and the ground to the motor. Could just corrosion on an old system.