I drove a 3 series car as a loaner once and that 4-cyl engine never made the oil temp gauge move in regular city driving, compared to my X3 35i, which gets the oil temp moving up much quicker. However if you have the dial to red, and the temp set to a warm temp, you should be feeling heat very quickly. There is a heater control valve that turns on/off coolant to the interior heater core that may be wonky, although they usually malfunction as a function of age. The dealer can sort it though. Good thing you are getting it in now instead of when it is zero outside!
