Car Vibration Coming From Engine??

[94BMW325i]

So when I go below 20 mph there is a vibrating noise that sounds almost like an airplane landing. I described it to my dad and bro and they say it is engine compartment vibrations. I am guessing the reason I can't hear it above 20 mph or so is because of the sound of the engine when accelerating. Is there a common piece of plastic that can become loose in the engine compartment?

Oh yeah I drive a 94 325i.

[Caps]

check that all the blades are on your motor fan. If a blade or two breaks off the imbalance causes the motor to shake/vibrate.
I had the problem on my 1994 325i, blades started breaking becasue the housing on the radiator/fan came loose and came into contact with the blades. Car had a terrible vibration and once I changed it, the car felt very smooth. Cost of Blade from the BMW Dealership (in South Africa) $27, Had it fitted in myself which too about 30 minutes.

[93 325i]

Sounds like your Guibo (Driveshaft flex disk) is shot. You are definitely due to replace that being you have a 94.

[94BMW325i]

Someone also said it had something to do with my alignment because I need new alignment.