golf mk4 s reg, over revving help!!?

Hi i have a mk4 vw golf s reg, the problem i have got is when driving up through the gears and accelerating, and when the revs go over 3 thousand they start shooting up quickly even though im using the throtle normally, its as if something isnt biteing properly. This happens nearly every day but now and again it will stop. if i use the throttle very very gently and keep the revs very low its not as bad but still anoying as hell!! ive been told by numerous mechanics that it will have to be booked in during the week but need car for work so need some ideas, and if i can fix it myself any ideas any one?? thanks Barry