After a cold start, I hear a loud single clunk/thump that sounds metallic after a cold start. The strange thing is it is coming from the rear of the vehicle. Anyone experience anything similar or know what it may be?

exhaust hitting against something maybe?

But why would it only do it sometimes?

maybe because sometimes the car starts hard and jerks the exhaust enough to make the clunk sound?

my vote is the exhaust/muffler/tip hitting something when starting.