Yeah, I had this at 85K.
I have a thread on a hack fix but definitely do what
TopJimmy is saying and vent the oil cap. If you hear a loud hiss and the sound goes away there's a good chance the diaphragm is ripped and stuck in the closed position so your engine cannot properly vent. It's a really questionable design on BMWs part especially with the failure rate (seems to be EVERY car) but then again it's guaranteed revenue down the road for them.