was the shop you took it to a bmw shop ie dealership? If they did inspection 2 of all things they should have at least hooked it up to the computer and check for any fault codes or if you have any friends that have a scan tool for bmw let them hook up and see if any fault codes come up or take it to a autozone its free to see if any fault codes are stored in its memory. its really hard telling what it could be at this point what did they do at inspection change anything? parts?