Hi chaps i had the same problem so i changed the gauge and it rectified it, for about 50 miles! So i suspected the new gauge was faulty, replaced it again lasted abou 100 miles!!!!
Stumped i was check the wiring and traced it on the wiring diagram ( by the way the resistor is in the temrature gauge itself) no faults.
Me thinks must be the vibration from the engine, no cant be how rubbish is that idea
Spoke to a very good main dealer and yes you have it, it's the vibration from the engine
Sorry cannot be more helpfull than that
