It's odd because it always makes that sound to some degree, but more so when it's between 0 & 8 degrees C. I have had it into the dealership 3 times complaining about it, and they say that they didn't hear anything weird/it's normal. I have only had time to drop it off before work and leave it, but I think I might bring it in, and ask to test drive one on the lot, because I certainly don't remember hearing that noise when I test drove one before buying.
When you go in when it's making the noise, get them to sit with you whilst driving