Don't know if your model is the same, but on my 201 these are the three bolts that mount the recirculating ball steering gear to the chassis and they are accessible from the LF inner wheel well. IIRC the torque spec is 80 NM.

I've dutifully retorqued them when called for, but never found one to be the slightest bit loose. I'm not sure why Mercedes calls for this - don't know of any other OEMs that do, so it's probably not a big deal.

Sometimes traditions die hard.

Duke