This is impossible to say without a physical inspection. Two different things can cause " loose" steering. Worn steering components will result in one or both front tires steering in a different direction than that dictated by the steering wheel position. That can also result in a tire wear pattern on one or both tires. That's one clue the person inspecting the car will look for.
One thing you can check yourself is to watch if both tires turn at the same time when a helper turns the steering wheel a couple of inches back and forth, and if the tires respond instantly when you turn the steering wheel slightly, or there is a delay before they start to turn. Identifying loose or worn parts is a standard part of performing an inspection before doing an alignment. Any tire and alignment shop will be able to identify problems related to those parts.
A totally different cause of a loose steering complaint is steering wander which simply means you have to constantly correct the direction of travel. That can become very tiring and irritating. Tight ball joints can cause " memory steer" where the wheels tend to stay in the position you last turned them too. After turning a corner, for example, you will have to pull the steering wheel back to center.
Another cause of wander is insufficient " caster". That is one of the three basic alignment angles. Think of it as the rake of a bicycle fork for the front tire. It doesn't go straight down. The fork tilts backwards on top. That, along with your body weight, is what allows you to ride no-handed. That is also what helps the car tend to want to travel straight ahead. Mercedes calls for extremely high caster values compared to other vehicles. 11 degrees is typical compared to the normal 2 - 4 degrees. This increases road shock and steering effort, but it is necessary to prevent wander.
August, 2, 2013 AT 8:29 PM
Usual side to side looseness can be traced to a steering shaft coupling beneath the brake booster. Coupling rubber bushings deteriorate. Cost about $150 plus labor. It is a pain to replace. Check MERCEDES FORUM. Lots of good advice and free.