Is it rack dampener adjustment time?
 

Car: 82 300cd, 160k, freshly redone injectors (did this before though).

Scenario: shaking due to the engine

Conditions: smooth as silk when engine is cold, or up to when the oil (not coolant) gets to temp. Smooth as silk at temperature when AC is engaged. When Ac disengages, with at in d or n, get a shake - seemingly less in neutral.

Driving engine is smooth and quiet.

Does this mean it is time to work the rack dampener?

Try it and see. This isn't quite a crippling procedure if not done perfectly. Therefore, I don't think it would hurt to try!

Try adjusting it first, your car is exhibiting a classic sign that it (RD bolt) needs attention.