If it is a 2011 and less than 50K miles you have BMWs 4 year/ 50K mile bumper to bumper warranty so anything not normal can be covered. Strongly suggest driving some at the dealership to get a feel for what is normal. No one here can tell you what to look for regarding engine and transmission operation. You never said manual or automatic, 328 or 335. Do more research to understand the differences between those two cars and drill down to what makes sense for your requirements. Take your time, repeat take your time, and post what you observe when you drive the cars after getting some test seat time.
Again you have little to be concerned about since you will have factory warranty.
If you are not a DIY guy you need to establish a relationship with good independent BMW shop once you are out of factory warranty or better yet seek out a CPO car, Certified Pre-Owned which is at the dealership. That will get you 6 years from date of delivery and 100K miles coverage whichever comes first...