C180 kompressor tranmission

Hi all, I'm totally new and hope someone
can help. I recently bought c180
kompressor auto s/c control 2005 model
170000klms full history very clean. Drive
perfect for few days but now Tranmission
is playing havoc!! It started by, when
selecting D it would clunk into gear and
might not change gears and if I stopped
and tried to select R or P it would not go
past N position and if it did clunk also but if
I switched the engine off I can select P no
problem.   I changed the tranmission
oil/filter seemed a lot smother but problem
was still there. Then I changed the 13 pin
tranmission adaptor but there seemed to
be mininal oil in the plug. After this It drive
perfect for one day. But it's playing up
again with the same problem.  What I did
notice sometimes it will not show either the
c or s mode nor can I select them button
does nothing and this is when the problem
happens and also when driving in D it will
show on the dash that I'm in R or P and
vice versa and won't change up or can't
select any mode. But if I stop and remove
key and restart it might show c or s and
drive perfect. I also did the tranmission
reset holding the throttle down system but
no luck.  Could this be a electrical
problem??   Any help much appreciated.
Thanks Gax