Metallic rattling under my '06 Tacoma

Have a '06 Tacoma 4cyl, AT, extended cab I bought new. Few yrs back, started hearing this rattling under the truck. I thought it was maybe a loose heat shield on the exhaust system. I checked, everything seemed tight. The rattling kept on, till one day it stopped. Now, about 2 yrs later suddenly the rattling is back. Anybody have this problem or knows what causing the noise.

 

It could be a number of things and the best is to try and replicate it and then find it with the help of someone and process of elimination. Rocks on skid plate sometimes causes rattling.

 

loose heat shield

 

I had a similar sound and too thought it would be a heat shield, but it was an exhaust clamp on the cat converter that broke and was loose, rattling around.