now what??????

i started my car after work yesterday and i can hear this rattling noise from under my car, i was thinkning maybe the heat shdild or something but what doesn’t make sense is that when the car gets warm(after 10 minutes) the rattling basically goes away.Now i knkow it’s something under the car cause i hear it doming from under the stick area.Anyone have any idea as to what’s rattling and how i can fix it.I am going to a muffler shop after wokr to see if they can help, but of course i thought i would check with you guys first.any help is appreciated

maybe one of the exhaust hangers slipped off and the pipe’s rattling on the shield?
Sometimes the engine runs a bit smoother after it’s warmed up, so it might not vibrate as much when it’s warm…