The car shakes when it is at a stop. What could cause the car to shake?

Power?

your passengers are gettin' jiggy in the back seat?

Your stereo is too loud?

Your engine's missing at idle?

Your A/C compressor is about to die?

You haven't tuned up the car in 12 years?

give us a little more info bud, we might be able to help. What motor, what codes?

Loose motor mount maybe...