Sorry for the question but how/where do you adjust the anchor shoulder belt? (2006 s500)- Thanks

You can't. It's tied to the seat movement. Move the seat forward will lower the belt anchor, and backward will raise it. It's a simple cable pully mechanism

Hmm, this is interesting. Front driver and passenger seats are at the same position but the shoulder anchor position on passenger site is a lot higher than the driver side. I need to raise it up (my side) because it is at the lowest position, it is too tight on my shoulder.

raise headrest

The anchor on the pillar post (behind the seat) can be raised just by pushing up on it (as discussed in your owner's manual).

None of the suggestions works. Skylaw, I can push the anchor up but it will not lock at the up position. Something may be broken in my car?