Comment by foobazzy

I was about to say the same thing. My car (nowhere near as nice as a Merc) had the same issue. There would be oxide deposit on the contact points and the minuscule amount of rust and crack on the clamp would render it useless on a bumpy road randomly (1 in 10 times approx). It was scary the first few times but when I figured out the symptoms, it took me less than a minute to get it to start.