Can you feel a bit of a click in the steering over bumps or when turning corners? A little play on center? Might be the steering spline wanting some fresh lube. Seems to need doing at 50k miles or so. Here's how:
1) Remove the under dash panel on the driver's side by removing the 5 T-30 screws. The OBD connector stays attached to the car - the wire is really long so you can pull the panel out then push the connector back under the dash while you work.
2) The white clip on the left should be in the hole in the panel, mine was not installed correctly. You may need to unclip it to remove the panel. Also remove the screw-on retainer holding the carpet in place.
3) Here is the culprit. This splined joint wants grease - thick, heavy stuff like wheel bearing grease.
4) Fix the steering wheel in place before you remove any more! The wheel can spin freely when disconnected and will damage internal wiring.
5) Remove the bolt (13mm socket, 3/8 drive ratchet, 6" extension) and pry the connector up to disconnect the steering linkage from the steering rack - I used the ratchet handle.
6) MARK the splined joint so you can replace it in the same spot. Pull it apart. Clean up all the old grease as well as you can (don't muck the carpet....) and regrease heavily - you want all the splines greased.
Now, put it all back together....
This is a regular maintenance procedure on both my 9-5s. Takes me about half an hour.