It probably just needs new plugs/coils. Most misfires are due to this. If it's persistent cylinder 5 I'd replace all the plugs first (likely can get this done as part of your 30k service), if you keep getting a cylinder 5 misfire, get the code stored and then de-mod it and take it in and let them replace the coil.
On the other hand, the coils are only 40 bucks.
GROUND CONTROL | STOPTECH | VRSF | COBB AP | STETT | OS GIKEN
2008 E92 335i MT