is there an easy way of fixing this problem, or do I just need to get a replacement cable?

Thanks

Michael.

Hi
it depends on what is causing it to be sticky in the first place, to start with check that the cable is routed correctly and if you have bar ends fitted that the one on the throttle side is not interfering with the throttle tube/grip, then lubricate the cables and see if you still have an issue.
bazz