Hey, at least you asked before you started complaining!
Lots of stuff will make the steering "loose", you will need to determine the exact cause. Since it is only in the center position, two things come to mind at once -- steering coupler and over-center adjustment on the steering box. If the coupler bushings are gone, the steering wheel will rattle on rough pavement or gravel, and you will be able to see the steeing column side moving without moving the steering box side. Gives about an inch of play.
If the box needs adjusting, the coupler will be tight, but the wheel will turn slightly before the pitman arm moves.
The steering on the MB big cars is a little "numb" right at center. Keeps you out of the ditch if you sneeze at 140 mph.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!