Shifting to 2nd gear
 

Model is c200 cdi-w203 from 2000 year. Sometimes, specially when car is started shifting to 2nd gear is hard, but after a while its almost normal. Same is from 1 to 2 and from 3 to 2. What could be the problem, should i change the oil in the gear box, because it has never been changed and there is 230.000 km.
Please anyone.... Thank you!