My 300SE W126 with 115K miles had this irritating sound - except I don't hear it while braking. The noise was most apparent when going through a speed hump.
Did all that was suggested here, in particular - replaced bushings, and the noise has gone down by 95%. There is a remainder 5% - pyschological [b/f].
126 tailed by a 203, 129 leading the pack.