Hi. My car (2001 E46 330Ci) has been doing this for a while and I did post something about it before. The scenario is that from cold it normally will run perfectly, no problem. If I then turn the engine off, leave it for say 30 mins or so and go back to it, it will not want to start but eventually will and will run rough as you like and won't really want to rev. The problem normally does not happen when it is cold weather and the engine will cool down quicker, when it is sunny it will do it all the time. I had it scanned and it came up with cam inlet sensor and one of the post exhaust lambda sensors. I had the cam inlet sensor changed and car was fine for about a week but now it is up to is old tricks again. Had it scanned again and the same 2 codes are coming up, cam inlet and post exhaust lambda. I spoke to BMW and they were useless, then spoke to an independent BMW garage and he said it could be something to do with rubber seals on the EJR valve or mass air flow sensor/meter? What do you guys think? It is driving me mad and I'm spending money and getting nowhere. THANK YOU!