Sounds as if the intermittent wiper relay is bad. The relay panel is above the driver side kick panel, above the fuses.
The wiper relay is #16, it is just to the right of the convertible top relay which is the only double-sized relay in the panel.
First try pulling the relay and re-seating it. If that fails, replace. In fact, if that fails, report back here.
There is a relay available from VW which will give you variable delay from 1 - 180sec (IIRC) instead of the pre-set fixed delay from the OEM unit. You program the desired delay through the wiper stalk on the column (and can change it at any time). It costs about the same as the OEM replacement and is a direct plug&play.
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