I had to tighten the rear outside door handle on my '91 300E. Actually not too hard: You have to remove the inside door panel with remembering that after all the handles and hardware is removed to lift the panel up. Undeneath is the moisture barrier plastic. Peel gently as it will rip easily. Best to only move the section by the door handle. If I recall correctly, you should be able to see the forward bolt head and almost see the rear one. (it has been sometime since I did this). I want to say the bolts are 10mm and might require both an extension and maybe a swivel to reach them. Make sure the handle is centered in the door before tightening. DO NOT OVER TIGHTEN. Firm and snug should do it.
I have had door closing issues as well. I have checked the striker plate to make sure it is closely aligned with the door latch. I have then used silicone paste that comes in a tube. Just a little on the stiker mounted on the car body. It has worked well.
Now ... the steeing column. I haven't a clue. I would start by lowering the under dash panel and seeing if there isn't anything loose. Also have you checked to make sure your under engine belly pan is attached firmly?
Hope these help.