Need help

[risky]

Today I noticed that when my car is in park it starts shaking and then stops and then shakes again and stops (on and off). But when I put it in drive it doesn't shake it's nice and calm. Any ideas on what it could be??

[Mebot]

Could be any number of things.. COPS, MAF, vacuum leak... how many miles on the car?

[risky]

It haves 88k miles. The cops have about 15k on them I bought a new set from musclemerc. I will check if I find a vacuum leak somewhere