throttle cable?

Hi ppl, not sure exactly what the problem is. Basicly i am having little problems with my throttle cable. 80% of the time it slighlty revs on tick over, if i put my foot under the accelerater and lift up it drops back to normal tickover. I dont actually feel it lift any at all, but it could if very minor i suppose. Do you think it could be the throttle cable sticking or some other problem. Any help would be great. Thanks in advance

Richard