I would replace the relay... sounds like it is sticky and trying to work but
cant at first so it draws more current then unsticks and works...
Kinda like when you use a hair dryer or something like that in the house socket
and the lights dim a bit when you first turn it on... It draws a lot of current
causing a voltage drop which dims the light in your house... in a car high current draw equals voltage drop which kicks in the alternator to compensate for the voltage drop... hence the ALT light coming on.

worth a try and probably cheap.
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vw bus site - http://www.geocities.com/vw_bus_74/index.html