As the title states it almost feels like a light misfire. No smoke nothing else weird and ill be checking the cam the end of the month some time. But usually cam is an issue all the time not intermittently.
Over the past several weeks I noticed on my 2005.5 BRM that it also had a rough idle (almost a miss), especially when it had been driven for a while
and was warm.
I had replaced the cam with an OEM one just over 100K ago, and the timing belt was replaced about 40K ago (when I set the torsion value to .5).
I checked the torsion (KW) value this week, and it was 0.0, so I reset the torsion to 1.0, and have noticed that the idle smoothed out.
I also checked my cam (had not checked it since I installed it), and the chamfer looks and feels good (I was worried, since I have read that OEM cam replacements will wear out).
Bottom line, I would use VCDS and check/reset the torsion timing to 0.0 to 1.0, and also check the other items that Oilhammer suggests.