New owner here: Sometimes when my 2006 E350 is sitting idle in the garage I hear a noise from the engine area that sounds sort of like my stomach does after 4 or 5 beers. Is this normal? The noise, I mean.

 

probably your brake system does it. that is normal. pop up the hood and behind the right headlight your gonna see your brake unit. SBC put your hand on it and if u feel it vibrating when u hear the noise then it is normal.
if not,can be the air pump,too. that's also ok if the engine light is not on.