Worn floating pins will cause the brakes to "clank" when applied, and the pads will wear tapered from front to rear (not top to bottom).

I suspect your problem is REAR rotors -- if they were under minimum thickness to begin with, they were bad, and if had them turned, they are surely too thin now even if they weren't to start with.

Check the REAR rotors for runout -- they will make the front brakes act funny when they get synchrnized right. They also vibrate badly themselves. Check the rear pads for excessive wear, too -- if you have a stuck piston, it will be on the rear. A stuck one up front you would certainly notice, the car will
"dive" badly to one side, even with zero offset steering. Quite a ride, if you've not had the experience.

Also, make sure the rear pads haven't collided with the anti-rattle spring -- this will cock the pistons in the bore on the caliper, causing drag, hard pedal, and eventually warped rotors. You will have to rebuild the calipers if they are stuck -- usually the dust boot is gone, and the piston and bore must be cleaned before they work correctly, and it's silly to put a used seal back in.

Did you use OEM pads? Padgid, Textar, ATE, Teves are all OEM. Most other pads will cause squeaks. However, a stuck piston can cause OEM pads to squeal, too -- so will corrision and dirt in the pad slots.

You may also have something loose up front -- vibrating brakes isn't a common complaint on the W124.

And last, did you rough up the front rotors when you installed them (or did the shop?). W124 rotors are turned, not ground, during manufacture, and there is a distinct spiral left on the rotor surface. If the friction surface isn't roughed with coarse sandpaper, the pads will groan for some reason, and this may both wear the pins excessively and cause the rotor to get "wavy".

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!