Audi 80 b3 2.0 sport running issue intermittent idling hunting

Hi there I have a mint 1991 audi 80 sport 2.0 8v engine code AAD .only 55k from new.with a intermitant idling issues has gradually got worse over time.can be idling fine the revs will start to hunt up and down really bad. will drive jerk when driving when does it. but no loss off power at al.you can turn engine off and restart 9 out 10 it will idle fine again any ideas please help me.thanks