The first thing to check is the transmission fluid, both condition and quantity. Take it to a good MB independent specialist who will have the equipment and knowledge to do it properly. I'm pretty sure someone from your part of the kingdom will be along presently to reccommend one. Don't be tempted to just add some yourself, the right amount and specification are critical for the correct operation and longevity of the transmission.
Top tip:- put the year of your car in your profile alongside its type.