Gear shift from 2-3 and 3-2 on 2007 Mercedes-Benz ML320 CDI

The car has 110,000 mile. I change the trans. fluid and filter every 50,000. At times (twice a week-drive 35miles to work and 35 miles home everyday) the car does not shift from 2-3(at about 40 mph and 2000rpm) the tach goes upto 3500rpm. The only way to return to normal shifting is to stop the car. Shift into park.Turn the engine off. Remove the key. Put key back in. Start the engine. Put car in drive.

Asked by for the 2007 Mercedes-Benz ML320 CDI
I have a similar problem when I drive fast. The gear is not shifting to 3 and RPM goes up to 3500, then I reduce speed and the gear shifts to 1. I am also curious to know the reason.