I have this same problem, can anyone tell me what to do? I have a 06 plate A150 and in the cold mornings the 1st, 4th and reverse are really stiff! You have to put the car into other gears before it will accept the 1st gear! When it warms up its fine! Mercs themshelves charged me £116 and no improvement, they greased the gearbox? What shall I do now?
No problems at all here after 3 years trouble free motoring. Way better quality than the average Ford or VW ( Pffft).
Ours had some recall work done during the first service, they put a drain hole in in the clutch bell housing. maybe rusty input shafts are a result of moisture build up on unmodified cars.
Ask if yours has been done, if not why not?