Add a little at a time. The only way to determine if the torque convertor has fluid is when the car starts to move. Once the car starts to move take it on a slow drive and take some ATF with you. If the trans shifts fine on your drive then the fluid level is OK. If not continue to add small amounts of fluid until the trans shifts OK (this is presuming that the trans shifted OK before your initial change of fluid. Once the trans is shifting OK, drive the car for about 5 miles to ensure that it shifts through all gears including reverse. Once you are satisfied that shifting is OK then let the car idle for a few minutes, check the fluid level with the dipstick while the car is parked on level ground. Remember the trans must be warm in order to get an accurate reading on the dipstick. Adjust the fluid level as necessary.

Sun Valley Mercedes Transmissions has an excellent website with lots of tips about Mercedes transmissions. They are located in Van Nuys, Ca.