I only have about 500 miles on my 05 6MT sedan. I noticed that while the car is running and for about 5 minutes after I turn it off, there is a "clicking noise coming from underneath. It's pretty audible - I can't hear it while I'm driving, but if I stop, have the window down, and no radio on, I can hear it.

Any ideas? I don't think it's a gas-related knock, I haven't had a car knock in years, but I think of a knock as when it seems like it won't turn off for a while. I've only put in one tank of gas, Mobil - 91 Octane.