P0303 Diagnostic and Fix for 2001 Jeep Cherokee Grand Laredo 4.0L Engine

Hi everyone, I'm Kevin and I recently encountered a code issue with my 2001 Jeep Cherokee Grand Laredo equipped with a 4.0-liter engine. Last Saturday, I drove about 20 minutes during a hot day with light traffic — the car was running smoothly and all fluids were at proper levels. After dropping off groceries and returning, I tried to start the vehicle again, but it barely started and ran very roughly, almost failing to idle properly. When I pressed the accelerator, it felt weak and nearly stalled, though it eventually stabilized and has since run normally. Today, using my FIXD diagnostic tool (which I plug in regularly when stopping at lights or after driving), I received a P0303 code: 'Cylinder Misfire Detected' with a severity level of 5 out of 5. Notably, the check engine light is not illuminated, and the car currently starts and runs smoothly. Given that my vehicle has 178,757 miles on it and I haven-'t replaced spark plugs or wires in years since purchasing it from a neighbor, I'm considering replacing both components with new spark plugs and ignition wires. I plan to use solid-core spark plugs — Champion brand is recommended for reliability. Any advice or insights would be greatly appreciated, especially regarding potential underlying causes despite the absence of a check engine light.