Speedo bouncing about 2.0HDI

[Martinez]

Went out for drive this morning and first noticed a mild surging from the engine. When I looked at the speedo the needle was bouncing about all over the place, even going from zero to 100mph. After few miles more all went back to normal. 
My first thought was speedo cable sticking, but tbh I thought they were electronic? 
I’ll have to investigate more, but anyone else had this happen ?

[cancunia]

A common problem with the speedo is the electrical connector on the speedo drive gear. It's on the right side of the gearbox somewhere near the right driveshaft.