Welcome, and enjoy your 300E! The search for words like 'warm', 'idle', 'start', '300E' will turn up a lot of threads - one of the better is 300E rough starting when warm. . .
. It also has links to threads by Benzmac on this issue in the responses, so click on those as well.
Enjoy your ride!
2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)
Click to see 87 300E