My 127,000 mile R129 SL ( that uses W124 bits ) has an increasing metallic rattle / click in the front. Ball joints / upper strut mounts are 4,000 Mi, tie rods are fine, steering box does have some wear. The noise has increased slightly after each track day and autocross I've run.

It has the classic feel / sound of a worn internal upper strut bushing. The strut / shock action is just fine and will be since the piston sealing band is still good enough.

The strut bushing wear as the suspension goes up and down, as the car is steered and under braking. Under braking the strut body tries to rotate forward increasing the bushings load, couple this with some bumpy road and wear increases.

Checking the strut is somewhat difficult on the car. If the suspension is left to hang the system tends to bind, if on it's wheels there isn't enough room to grab the strut body and shake. You would want to move the strut body left and right then front to back. This bushing is part of the strut and can't be changed. I don't worry too much about bushing wear as nothing will fly off and the strut will start to leak long before the play gets enough to worry about.