Dakota is correct about how to check for codes on your car. Follow the instructions in the link he provided. If you have checked the plugs, wires, coils and ICM (module behind the coils) your problem could be fuel related. If the fuel filter has not been replaced lately, replace it. Have your mechanic check fuel pressure are the fuel rail. If it is low you probably need a new fuel pump. If the fuel pressure is good, you may have a bad injector. You need to know which cylinder is misfiring. Get the trouble codes and post them for us to review with you.
2001 Bonneville SSEi (retired at 365,000 Kms.)
2014 Jeep Grand Cherokee Overland (yes, I know its not a GM)