Mercedes C350 2010 - Limp and only changes to second @ 3000 revs - what's wrong with it?

Mercedes C350 2010 - This car seems to have a gearbox problem of some
sort. The problem is intermittent - but now and then when I drive it from
standing still, the car will rev to 3000 revs before changing to second and
have no power. There is no warning lights, no engine light, but the car is limp
and has this high gear change from 1st to 2nd. When I park and start it again
later, it might be that way, or it might not come back for a few days. Any ideas
what this is about? The car has around 64,000 miles on it and a full-service
history. I've also had the car's log looked at and nothing has really come up
there that explicitly points out what the problem is.