Engine Rattling Sound

Hello- this is my first post.
I recently purchased a 2005 Pacifica AWD Touring with 13k on it.  After driving it for a month or so, I started hearing a rattling sound in the engine that is there when the car is idle and  moving.  When I accelerate the rattling sound increases in speed as well.   My wife says the car sound like old clunker.  Although the rattling has not affected the performance, I am concerned that this could be a bigger problem that needs attention.  I've gone through some of the previous posts and found many refering to a "clunking" sound, which I don't think this is.  Has anyone else experienced this engine rattle?   What would anyone suggest I check out?   Any help is appreciated.
 
Thanks!

It is not uncommon that a heat shield will rust and rattle.  Check around the exhaust manifolds to see if any are loose.

Take it in to a trusted dealer. You still have powertrain warrenty. The 3.5L has been a bullet proof engine for Chrysler. Seeing that the noise is there at idle as well as when driving,suggests an engine related concern.

thank you for the feedback...I brought the car home and looked under the hood to see if I could isolate the noise.  Someone in an earlier post had mentioned that their oil level had gone down, and that this may have been the cause for the noise.  I checked the dip-stick and was shocked to see that I couldn't see much of any oil on it.  I immediately took it in for an oil change and the rattling disappeared.   Although I am happy that the rattling is gone, I am now concered how it would have lost the oil.  There is none on my garage floor. 

I scheduled an appointment with the local dealer to have them take a look.