Miss Fire on some starts

[03silvertiger]

So I m getting a missfire. IT only happens once in a while. IT takes a couple of starts than seems to stop, I m not sure whats going on new coil new wires new plug new 02 sensor. Car has 242000 on it. Once it smooths it drives fine. But it does seem like its lasting longer each time it misfires. Any ideas? Could my coil gone bad again?? I sea foam my car about ever 9-10,000 miles. Timing belt tensior? Let me know what you think.