1999 3.8L intermittent P0303 code

194000 miles, this just started a couple of days ago. A miss at startup then after several seconds it smooths out. It's intermittent (doesn't happen at every startup); the code is a P0303. Any suggestions?

P0303 is a #3 cylinder misfire, more than likely caused by a defective ignition wire, plug, coil, or fuel injector.