car over revving?

i have a fiat bravo 1.2 and it keeps over revving it only goes to 2000 revs but doing my head in it happens when i first start it and when im at a stand still italso has happend when i am driveing anyone now how to fix this pls it also fells like its going to cut out sometimes and when i put my foot down it jerks a bit like the petrol is going but petrol is fine and only happens now and again