petrol needle playing up help please

[tacka]

hi i have a 1999 audi 80 1.8 cabriolet.

just this week i noticed my petrol needle not displaying the proper fuel in the tank on occasions. It would go down a quarter of a tank and rise up eventually again.

However last night the needle completely failed and dropped from a half a tank to empty working so when i completed my journey i switched off the car and lights, restarted the car and the needle on the petrol gauge worked again.

i heard this can be a common probs on audi's any help to resolve this?

thanks