scott 20v

On my 20v coupe quattro with 7a engine, the oil warning on the self check has started to come on when I switch on the ignition. The oil pressure gauge also shows about half a bar with the engine still off. When I start the engine oil pressure rises and light goes out as normal. Any ideas??

Help!!!
I have a 1990 20v coupe quattro.
I get loads of transmission shunt, Banging sound and gearstick moving, when pulling away in first and when applying/coming off the power when in fifth.
I've just fitted a poly rear diff mount but It's still the same.
Does anyone have any idea what could be causing this????
Thanks.