Weird issue that started last winter, when it is below 32 F outside and i start up the car it makes a terrible metal clanking sound. Like somebody is under the vehicle clanking a screwdriver around under there but it only last for about 10 seconds or so then stops. It only does it when its 32 F or under. if its in the 40's or so nothing perfectly quiet, so it started last winter towards the end and it went all spring and summer and fall no noise whatsoever. Now its winter again and the noise is back. Its hard to narrow down where it is coming from because it echos, but general area is exhaust manifold and transmission case under the car. Any ideas? Car is a 2010 murano with 170,000 miles on it.