One problem related to air bag on-off switch has been reported for the 2011 BMW 328. The most recently reported issues are listed below.
At temperature above 87 degrees f (after a full day in open parking lot under sun) as indicated on the car's dashboard, the seat belt sensor of the car malfunctioned. Even though I had my seat belt firmly clasped but the car kept on beeping seatbelt warning for about 5-10 minutes until the temperature inside the car dropped to less than 87 degrees f. The seatbelt warning went away after I opened the window and let the car cool down or switched on ac in the car. This is a repeatable problem and can be reproduced if my car is kept in direct summer sun for an afternoon and has occurred a number of times in the past. Since airbag sensors interact with the faulty seatbelt sensors so it has potentially serious safety consequences and need to be addressed by BMW as soon as possible.