Code P303 misfiring and engine light is on

I have a reoccurring problem with my engine light appearing causing my car to lack in power, misfire continuously and eventually causes my car to come to a complete stop. I then turn off the car turn it back on. The engine light goes and car works okay with a slight misfire.I diagnosed my car finding P303-cylinder three misfire. changed all the spark plugs and the cylinder three ignition coil. I am still getting the engine light coming on and causing my car to run really bad whilst the engine light is on, but when I turn off the car and back on the engine light goes and the car runs fine with a slight misfire. can you please help me?