I hear a rattling sound in the engine when the car is first started. The rattling goes away after the car has warmed up.
Honda has a service bulletin out for this specific complaint of a rattling noise of the engine during warm up. The bulletin number is 07-028 and it refers to having an intermediate heat shield replaced with an updated part as outlined in the bulletin. My recommendation, if you are no longer under warranty, is to have a mechanic, such as one from YourMechanic, verify the noise and replace the heat shield as outlined in the technical service bulletin.