Engine start up noise

I have a 2003 Chrysler 300 M V6 with approximately 55,000 miles on it. For the last 4 to 6 weeks when the car starts cold or after several hours of sitting something under the hood sounds like bearing growl and tappet noise for 1 to 2 seconds. Then the noise stops. Engine oil level is fine. What might be the source of the noise and how might I deal with it.

It might be the decoupler on the alternator pulley.