help with my mk2 golf 1.6

right can be driving along all fine normal temperature then the engine will start to back of as if its starving itself of petrol hestating basically can sometime go if i bury the throttle to the floor it clears itself other times it keeps losing power till i pull over shut it down count to 20 restart is then fine and running sweet pissing me right off any ideas am about to start smashing it with a hammer unless i can get it fixed so any help would be appreciated