Squeaking / shaking under the hood

When I have my car in Drive and have the brake down, it squeaks like something is shaking back and forth. I also hear itin reverse but not in park. When I looked under the hood while someone kept it in drive, there is a box next to the battery that shakes around. Not sure what it is. Could it be the air intake shaking. Any suggestions?

Grab onto that box and hold it. Does it stop squeaking? You found the problem.