Noticed last night that the speedo needle was jumping all over the place.

It'll hold on a constant speed for a short time but then will jump about wildly.

Sometimes up sometimes down.

Alo more noticable at higher speeds of over 50 mph.

I've had an issue since I bought the car.

When I'd start it it would jump then drop back down sometimes.

But has always held speed perfect.

Is it a bad earth maybe?