I have a 2010 nissan altima coupe, 2.5L. Whenever i accelerate slowly the car rattles and vibrates at around 1900-2000 rpm. The car is in great condition, I have 110k miles on it. I saw in other forums that the exhaust hanger bracket could be the source of the vibration. Some people replaced it and the noise went away and others put washer bolts in between the frame of the car and bracket and claim that the vibration went away. I put the 4 washers on it and i do feel a small difference in the harshness of the vibration. Is there anything else that could be causing this?

loose heat shield on the catalytic converters maybe?

Typically a vibration to create rattle is a harmonic inspired thing if specific rpm based. Meaning anything and anywhere on a car where there is unsupported extension of a source that can rattle the noise can happen. Any part that can line up in sympathetic vibration can make noise too. That means about 500 different parts on a car can do it.

You have to chase down the noise and location to figure out what to do to stop that sympathetic movement.

My Versa has vibrated to make noise at the glovebox, a door panel, heat shield underneath, a/c bracket, exhaust mount point, trunk lid, and will probably several others before it dies.

The condition of engine mounts can make that better or worse.