Thanks for your quick reply, Doug. It bomb starts quite well. I don't think it's the starter, though it's hard to say. I had it replaced twice within a 4 month period (about a year ago, but I have barely driven the car in that time). The battery is fine, from what I can see. Do you think there could be any connection between the fan and the starter? I know it's unlikely, but one never knows with VW.
I'll definitely try the shoulder belt thing. I'm trying to sell this car (I have put a shocking amount of money into it) and I don't want to saddle some poor person with this issue. Do you want to buy it?