I have a 96 a4 tdi an there seems to a shudder

Have you really stomped on the brakes lately, such as a panic stop? Did the vibrations start afterwards?

The most common cause of brake shudder is due to a warped rotor. Unless the rotor is catastrophically warped, you will not be able to see this just by looking at it.
A tech will often check these for free with a mic when you get your tires rotated.
If they are warped, and can be turned on a brake lathe and remain within the minimum thickness specifications, that is the easiest/cheapest fix.

A shudder coming through the brake pedal is the sign of a warped rotor. You say the rotors, pads, and calipers are fine. Did someone inspect them or do they just "look" fine? A visual inspection usually will not show if a rotor is warped. You'll need to have them turned or replaced to be correct the problem.