Sometimes when am driving, as i let off the throttle and begin to slow down the car kind of judders and then again when i start to put the gas on it judders again, but it only does it sometimes

Is there anything that i can give a good clean out or anything to make sure nothing is blocked or anything
Its on a s reg 2.0 sri so its getting on now, so maybe something that needs cleaning will help the car run abit smoother?

Cheers,
Mark