The idle on my 2001 E220TD seems to be a little lower than it should.

The engine vibrates and the condition is more annoying than concerning at the moment.

The speedo reads 750 max at cold, but if you touch the accelerator slightly to about 800, again reading from the speedo, the vibration disappears.

Is there a way of adjusting the idle speed or is it the sign of a certain component on its way out?

The car has full MB service history and currently has 125,000 miles on the clock. with the next service due in 2100miles time.

Any assistance much appreciated.

 

before would it idle at 750 rpm just fine? if it indeed idled fine at the rpm previously have you checked to see that one or more plugs have not failed?
is it related to the colder weather or was this occurring at warmer temperatures as well?