Grinding Noise from Fan

Really need to take this car to shop that has the skill to deal with the computer systems on your BMW, if the car dies, there WILL be codes to check, a shop should KNOW how to do this, or they aren't capable of working on your BMW which has up to 43 computers. I have worked on lots of these 2003 3-series. As for the fan noise, it could be many things, a glazed belt etc. The fact that it is coming and going may mean it is a glazed belt that is getting moist from the moisture in the air as it gets colder and then will be noisy, especially in the mornings right after start up. This should be inspected to make sure that you don't have a leaking water pump that making the belt noisy.