Rattling?

Is anyone hearing a rattling sound underneath the truck for a minute after startup? I started experiencing it a couple of weeks ago. Don't fret, it is going to the shop. I'm just wondering if anyone else is hearing it as well and what it might be. I'm not saying it is, but it sounds tinny, like a manifold shroud. I've looked but haven't been able to find it.

 

Heat shield?

 

That's what I am thinking, but I cannot locate the sound. It's loud so it sounds like it is coming from the entire undercarriage and only lasts for a minute so it's next to impossible for me to find the source. Just wondering if anyone has had the experience and found the source. I'd rather tighten a few nuts and bolts on my own than have the truck in the shop for a few hours while tech try to locate it.

 

Mine does the same. I can also hear hit over low speed bumps.