OK guys , problem with a 1987 300E, UK model.
Engine die's in the following circumstances,
At a steady cruise or normal freeway type driving , but if throttle
position is held , engine will pick up again after a few seconds.

City type stop start or slow-fast-slow driving , engine die's or will not pick-up when getting back on the throttle. Then when a re-start is attempted engine does not want to restart but does eventually after much cranking. Sometimes it is a clean re-start , sometimes missing and rough.

Otherwise the car drives perfect , that is, until the fault occurs the engine runs fine without missing or lack of power.

Just wanted to find out if some1 had a "I know what that is " cure before I go for a diagnostic.

I have checked battery cables , and I replaced the distributor cap as it needed doing anyway. Have checked for obvious loose connections etc.

Any suggestions would be welcome.