How can you tell if you might need an engine mount? Because I feel like the engine vibrates and it goes away, I'm used to feeling hardly any engine vibration.

 

1 - Lift up the hood.
2 - Put car in drive, hold brake tightly
3 - Have someone look at the engine as you give it gas (while still holding brake)
4 - Look to see the engine rock on it's mounts. The more it rocks the worse the mounts are.