Someone please help! Have a 2009 Chevy Cobalt. While driving the RPM's started Fluttering all over the place from 4k to 0. Then it dropped to 0 and stayed there. Service traction popped up. The engine didn't cut out. It stayed in low gear. While sitting in driveway, put car in park then neutral and then reverse it was shifting hard. Put car back in park and shut off. When started back up the code went away and shifting was better. Took car to a friend, who pulled and cleared the codes. Car has ran fine for @ 200 miles. Last night it started doing the same as above again. Any thoughts?