I've noticed recently that when im out on the freeway driving at 100kph (62mph) and then slow down to about 40-50 kph (30mph) the car starts "bumping" about as though there is a massive buckle in the wheels (which there arent). Its feels as though im riding along a corrugated-iron roof.

It only seems to be when im rolling, not whilst braking, and when i get up to around 60-80kph it smoothes out.

I had an alignment and balance done to no effect and my tires are fine (195/60/15's on stock steel wheels).

Im getting a suspension check-up on saturday but can anyone give me any other suggestions? (my springs/shocks are totally stock)

(its a 1992 180e (or 190e 1.8 in other parts))