As with everything Mercedes, use caution when adjusting the steering box. It can be adjusted, but do so in very small increments to avoid raising the internal friction to a point where it interferes with the normal free movement of the mechanism. If you check your manual you will see that there is a complex procedure for measuring this freedom of movement (internal friction resistance) that uses a small torque wrench on the steerting wheel nut, with wheels up, and the suspension unloaded.

That said, you can try loosening the lock nut, hold it with the wrench, and then turn the center screw anti-clockwise about 1/8 turn. Re-lock the nut and try the steering for feel and play. Remember, the adjustment to tighten, i.e. remove play, is anti-clockwise. It would be wise to apply reference paint marks to the adjusting screw so you can keep track of your adjustments.

There have been other threads that address this issue. A search may help to further clarify the matter for you.

Good luck,

230/8