Cars of all brands do go wrong though although I also would not be impressed if it went wrong after <100km. If anything BMW are likely to be less reliable than a Honda because there is more electronics and more cutting-edge technology in a BMW. Cutting edge can sometimes turn into bleeding edge....
Make the dealer give you a loan car at least equivalent to the one you bought and a no-BS explaination of what is wrong with it. I'd definitely want a no BS explaination and a talk to the mechanic who worked on the car + service manager. If it is something serious, I'd be looking for a new car as stated above.