I have a 2004 Vito that does the same and on occassion , it also locks the
key in the ignition switch and can't be removed on other occasions, I
happens with both keys I own and ther'e no pattern to it.

I've also been unable to get into the vehicle, the worst case was 20
minutes, it just wouldn't unlock, fortunately I was close enough to home to
go and get the spare key, which then didn't work either, then all of a
sudden the riginal key did work - no rhyme or reason.

I've come across two other Mercedes stuck in Petrol Stations (both saloons)
that have had a similar problem.

My dealer flatly denies there's a problem, and of course you can never get
the problem to re occur whilst at the dealership, I also happen to have a
host of other minor elecrical gremlins, some of which have never worked
since the day the vehicle was delivered, yet it appears Mercedes are unable
to repair them.

Which is why I'll not be replacing this vehicle with another mercedes when
the lease is up...

I also own a 1990 560 sec which has a metal key that you put in a lock and
turn it....has no electrical gremlins and aprt from being a little tatty (
repsray organised) is a fine car. Shame about the overcomplicated stuff.

Alan M

Thanks so much for the helpful responses. Wrencher, does the key
problem mean a replacement or is there a less painful workaround?

Ramapriya