1998 automatic punto?

....i have an automatic 1998 fiat punto...sometimes when i get in the car and put it in D i can not drive forward until i rev alittle and a red gearbox sign is lit up on the dash..sometimes the light will go off and then come on again [it does not flash] then i can drive normal and gearbox changes gears as it should,until i put it into P and start the car again to drive..
other times i can just get in and put into D and drive...please could you help me?
any advice would be great...
i have contacted so many people who have said all kinds of different faults...

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