Surging in cold weather?
 

I have a 97 E420 and the engine rpm is surging at idle from about 500 to 1000 rpm up and down, in cold weather only. When it warms up a little it stops.Any ideas would bee great. It starts happening at about 5 degrees. Is there anyway I can get any fault codes.

thanks.

Oh it doesn't quick when it warms up I drove it for 45 min. and it didnt stop.