1999 Wiper Issues

For some reason after starting the car and using the wipers for the first time, be it on intermittent or constant they keep working for about 10 minutes before parking after they are turned off. After that as long as the car has not been restarted they work as they should.
Anyone had similar fault and how was it cured?

Looking like a trip to the nearest merc expert as now the wipers stop when on intermittent after a few sweeps but they stop at bizarre angles on the screen and the period from them parking on initial start is increasing. Is there a wiper control module somewhere that controls this or is it in the actual stalk?