car shakes!! help!

I have a 2000 passat and when I turn it on, the car shakes/bounces a lot, and the rpms go crazy... it goes up and down (while the car is parked but on) then after a while, it stops and the car is normal. sometimes the car turns off while it's doing that. However, if I try to put the car in drive while it does that, my car won't accelerate. It feels like it's in neutral (the car is an automatic) and when it try to accelerate (while it's still like that), it jerks foward a couple times, until it finally stops and drives normal. then the check engine light comes on and the car beeps and says "emissions workshop" what in the world could it be?!? it's driving me insane and i feel like people are trying to rip me off!! please help!!

could be secondary air system has water in it and when you start the car up the water goes into the engine and causes it to misfire