Starts juddering when attempting to accelerate from a stop

I recently bought the car listed above cdti after it had been sitting in a car lot for eight months and I’m having trouble starting my journeys. It starts fine and sits in idle nicely, but when trying to pull away the revs do not build and the car judders. When I pull over, take it out of gear and rev the engine to about 4,000 or 5,000 a few times and then try to pull away it is absolutely fine. Is it just build up and needs a good drive or is there more to it?