What would cause a 2000 Mazda millennia to jerk?

I'm not a technician, but generally, spark plugs would be the first thing I'd think of. You should change them every 60k miles. Do you have a check engine light on? If so, take it to Auto Zone & have them pull the codes. You can also take it to the dealership have them do diagnosis on it. My dealership charges $99.75 for diag. Then, if a customer has repairs made, we credit 1/2 of that fee to the repair. Millenias are good cars, but they're pretty expensive to repair.