E300 TD 1999 stationwagon drive train/steering?

Hi,

My car has developed a rubbing/vibration on its left side (possibly front wheel) when turning right, when the car is cold, also in reverse. Mileage is approx 190,000 miles
Workshop has tested suspension, found nothing. Could it be steering gear, or differential? The problem disappears once the car is run warm. Tires make no difference (after replacement, things have not changed, except that it appears that balancing the wheels/realignment makes it disappear for a short while, i.e. about two or three days).

Any ideas as to what this could be?

Many thanks,

hsl

was the workshop a general repair shop, or a Mercedes specialty shop??