sputtering on 2005 Cadillac STS

When I am driving in traffic and Im coasting along barely touching on the gas I can feel my car sputtering in like 3rd to 4th gear and also sometimes I press on the gas it gives me a sluggish feel in the take off, what is that?

Asked by for the 2005 Cadillac STS
It sounds like your Cadillac STS may be suffering from an intermittent engine misfire. Is the service engine soon light coming on? If so fault code(s) will be set in the powertrain control module. The codes can be read with a scan tool an may help determine the cause of your problem.