Rattling sound while in park, slow driving, or idle.like something is loose

What is your question?

When in park or idle, and acceleration, once car has been warmed up, or when you start car or slowing way down like your pulling in drive, when you push on gas and barely tap to rev it it starts and stops immediately. it makes rattling sound on top of engine, rather loud, sounds exactly like vibrating loudly or like something is loose and rattling.we’ve check oil can’t find where to check transmission fluid it-started this 2 days ago but today it started doing it in drive if slowing to turn corner. Or slowing to park. No lights on dash drives great, little sputter like it’s gonna die when first started that started bout a week ago but only does little sputter in park, and it don’t do sputter very often. I’ve got no dash lights lit up and drives perfect, I want to fix, but also need to know if I’m damaging my car at this point to drive.

What makes this problem better or worse?