W123 Mercedes 200 cold weather bad running
 

Hello, can anyone please help me with the problem outlined below.

Throughout the warmer months she drives beautifully but now the cold mornings have arrived it does take a while to settle down. It will start on the button, but once driven for a mile or so it starts to struggle and it becomes difficult to keep the revs up and eventually will stall. If left for an hour or so and the heat has fully warmed her up she will be back running just fine again.

Many thanks for any suggestions, Chris.