There is quite a few amg cars that do that, normally aspirated and kompressor. I have done extensive reading on this and seems to be normal, loads of discussions on american sites as well. Mine does it as well once left for a prolongued period without use (other members' both e55s did as well and olly advises as normal) and sometimes at cold starts if the last use was a short drive before parking the car (it never warmed up fully). Went to London the other day, fast drive the car got a good run, left it for two days parked then no smoke. A guy with a clk55 mentioned it as well and c32s.
My car again does not smoke while driven and in the approx 4000 miles I have covered since bought there has been no movement on the oil at the dipstick not even by a mm. In my early paranoid days I had a mate drive in front of me and tried to keep up, asked him to keep a low gear at high revs, boot it, then back off, then boot it again letting it roll - checking for seals wear smoking etc - and no smoke, nothing.
It has been advised that the way the breather system works if there is enough fumes and carbon build up, the location of the pipe that helps the system breathe from the induction is above the intake and if it drips oil overnight the engine will suck it at cold starts.
It has also been very noticeable on the new slk 350, which when people spoke to dealers again it was deemed as normal. Similar smoking is also evident on e39 BMW M5s and e46 M3s. Videos also on youtube for this. There is also an e430 v8 on youtube that demonstrates it well on a cold start.
Some americans have recomended seafoaming the engine. Need to read more about that.
This is amateurish advice, but its from what I've been reading.