I did a little digging and lo and behold the problem is the stalk switch. The blinking stops if I tap at the base of the stalk a certain way.

It doesn't seem like a Mercedes turn signal switch should be so poorly made to break in only 107,000 miles, but there it is.

So now the problem is removing the air bag and steering wheel. I am not a novice but I have never removed an air bag equipped steering wheel. Any pointers in this direction will be much appreciated. I have the factory workshop manual on CD but I prefer real life experiences shared by experts on this forum.