Hi Sam,
you have got mail and now you have explained what, your problem is.
I guess there are three possible reasons for the temporary indicator malfunction:
1. Broken or short circuited wires
2. Bad welding points in the dashboard. This is a well known problem.
3. Bad sensor G2

@Bastian (why do we communicate in English?)
There are two sensors (G62 and G2) and one thermo switch (in the radiator):
G62 is for the motronic ECU only
G2 ist for the temperature indicator in the dashboard.
I guess (means: I DON´T know exactly), the switch in the radiator is an additional switch for the cooling fan. Maybe even for the highest revolution level.
The cooling fan is activated by the dashboard ECU, witch is getting it´s data from the coolant temperature indicator.

Beste Grüße
Tim