2nd gen rattle and clunk at low speeds no vibration felt

i have an 06 tacoma 2wd that is making a rattle at low speeds. I heard it earlier this week and it went away and now its back. I can only hear it at low speeds and i hear it the loudest when i pull up next to cars i think because it echoes against them. It's a rattle sounds like metal on metal is vibrating together but i feel nothing inside the truck. Also i have a light clunk at low speeds maybe 5-20 mph then i cant hear it. I just had my driveshaft rebuilt and balanced a few weeks ago and evrything was fine for a while until now. I think both sounds started. happening around the same time about 2 days ago. the rattle seems to be coming from under the drivers seat and the clunk is more towards the bed of the trunk. Any ideas of what it can be?

 

I had a rattle like that. Turned out to be the catalytic converter shield. I put a hose clamp around it and tightened down, went away. Might want to check the other heat shields as well

 

thanks for the tip im looking into that right now. also checked my transmission fluid level and its low. how can i know what kind of transmission I have?