I have a 1999 Mercedes Benz C200 with a general power problem. The exterior and suspension are in pretty good condition but the car seems to have a delayed response/ lag when I press on the throttle. Also, the automatic transmission seems to take a while to shift gears ie the gears shift at slightly above normal revs. I have had the car regularly serviced and checked at my local dealership and they cannot figure out the cause of the problem. In my opinion the throttle cable seems to lack tension but that would only account for the delayed response and not the other problems.

Is the above a sign of a bigger inherent problem? Does anyone know how to fix it?

It sounds like your throttle cable is stretching, or in some manner is about to become disconnected. The throttle cable position is also the cause for elevated engine speed when shifting. You might try adjusting the throttle cable to see if you can adjust the cable tension so that there is a lessor amount of free play. Do not overtighten. If you cannot find the adjustment problem, I would have a new throttle cable installed. Make sure that your Cruise Control is correctly adjusted after replacing your throttle cable.