Get under the car and check the 3 linkages between the shifter and the gearbox. I've seen one that locked up in 2 gears because all the linkages bushes were worn out.

If you find worn bushes then change them all, they are easy on W213's and they are cheap.

That's the best place to start.

__________________
Alex.

MB Tech
Sydney, Australia
Volvo 122S
W201 190D 2.5 manual
W202 C240
W203 C32