Since this is a Diesel car, I am not sure whether this would be applicable or not. But did you try cleaning the Intake Manifold with some chemical like Seafoam?
I have a Petrol 1.8L car and I experienced something similar when I try to pick up after being stationary at a roundabout or when joining the motorway through a slip road. The issue I had is related to the Intake Manifold which ultimately had resulted in low air flow to two of the cylinders. After replacing the Intake Manifold Runner Control (Vaccum solenoid) the car works absolutely fine now.
Ford C-Max Ghia 1.8L - 2004 : Manual Transmission