C220 cdi gearbox slipping

[didi w203]

hi. as title....w203 02 reg auto. .. slips when going around 35mph. had no drive after a 2.5 hour drive yesterday..stopped car restarted and was ok after but still slipped.....did a bit of research just need further expert advice. poss oil or magnetic plates? How do I check gearbox oil?
cheers in advance.

 

[didi w203]

Thanks for the reply.. any idea how many litres of gearbox oil it holds?