If you've not had the fuel system flushed, try a serving of BG's 44K fuel cleaner. When I bought my '06 S500 year ago, it would occasionally miss during cold starts and when idling. After two tank refills using BG's 44K mine began running a lot smoother.
I went several tank refills without using it and it began running a little rough again. Now I use it every third or fourth fill up to keep it running smooth.
I've been a fan of their products since 1988!