It is likely a bad ground. Usually if it is only one gauge it is the actual "pot" that controls the needle for that gauge. The "pot" is like a little coil in a metal cup that has a pin for hte needle to sit on in the middle, apply power and the coil rotates moving the needle. The amount of power determines the amount of movement the coil does resulting in the amount the needle moves. The back of the metal cup that holds the coil is flat and has two metal pins that fit into the circuit board of the instrument panel. One is for power and one is ground. Like the fuses in your car, the pins can oxidixe and reduce the ground, also they seem to lose a solid connetion and it causes thhe coil to waver or sutter, getting power intermittently. If this is the case with your cluster, a very likey answer is that the needle "pot" or potentiometer, needs to be pulled from the circuit board, the pins brushed with a brass or metal brush and then reinserted in the board, the contact will be solid and typically the needle problem goes away. I just did the repair on a guys cluster from florida and it was the exact same problem. Pulling the cluster is easy, dissassembly and pulling the pot off the board is tedious and requires pulling all the needles on that gauge, removing the face and pulling the pot off carefully, not for the meek of heart.
Not a guarantee this is your problem without testing, but if it is one gauge, the pot is my guess, I have seen it several times.
Good luck

__________________
Christopher Henkel
1990 190E 2.6 - Arctic white SOLD
1986 190E-16v - Blauswartze
1993 300CE - SOLD
2003 W208 CLK 320 Cabriolet - Magma Red