The car wont have leads, distributor, rotor or cap. The MB's use a semi-direct ignition system. Could be the plugs but if it hesitates then is OK it makes you think something electrical or ECU related causing a blip.
Is the problem conisistent or intermittent? I saw a similar problem on my father's W202 c220 (petrol) where the symptoms were intermittent. They did nto always occur when braking but also when starting up at times.
It turned out to be an ECU problem. What mileage is on the car?