You most likely need to replace you spark plugs. It is very possible that you need a tune up. If you are having this problem you may want to get a diagnostic test run and check the oxygen intake sensors.
First thing to check is the air filter the second is the pcv valve and the third is the fuel filter. If all of those check out ok then clean out the throttle body and pay close attention to the idle air control valve. Clean it out with brake cleaner and also clean the egr valve out too.
Start with the basics. Perform a factory suggested maintainence on your vehicle. This may include spark plugs, wires, air filter, fuel filter and battery. Next check for vacuum leaks form hoses or the intake.