I've had my 2008 135i for a couple of months now and one thing that it has done from day 1 is that on each startup I hear I hear a raspy tinny sounding rattle from the exhaust for about 1 second. There is no further sound once the engine is running or when I rev the engine. I also hear it very briefly on shutdown. I assume it's a valve opening (or closing) in the exhaust. Is this normal or is it anything that I should worry about?
Edit: Here's a clip I just made
Anyone elses do this?