One suggestion is to check the steering damper (shock) mounted in the steering linkage. Check for previous posts on this subject. I recall someone replacing one recently.
You can check by disconnecting one of the mounting bolts and checking the action of the shock.

__________________
1990 190E 2.6
1996 Grand Voyager 3.3
1985 Mustang GT 5.0 5 SPD
1982 Suzuki GS 750T