Most times a undercover cop will not pull you over and will wait for a marked police car to perform the traffic stop which is what they should do.
But if an unmarked police car tries to pull you over you don't have to immediately pull over but instead keep going slowly and contact 911 to make sure it's an actual police officer trying to pull you over.
The police officer in the unmarked car must also be in full uniform to carry out the stop of your vehicle.
If in doubt just call 911 to make sure it's a police officer who is actually pulling you over.
If you do pull over do not roll the window down and keep your vehicle door locked until you confirm it's an actual police officer which you can do by calling 911.