First I would get a can of Quick Start starting fluid(ether).
Look for where the Power brake vacuum hose attaches to the intake manifold or where the PCV Valve hose attaches to the intake, remove either one so you know you can do it then put it back on.
Then the next time engine doesn't start, pull off that hose again and spray some starting fluid into the intake.
Replace hose and try to start engine.
If engine fires up and dies you have a fuel problem, could be fuel pump relay or the pump itself.
If engine still doesn't fire then your problem is spark, ICM(ignition control module) on the front of the intake did have problems, also the wires for it would get frayed at its connectors.
Only the Exhaust side(passenger side) spark plugs and coil are used when starting, so if that coil starts to fail you would get a no start, you can swap coil positions to test that.
There is also the Crank position sensor, but these are rarely intermittent, it tells the ICM when to start sparking the coils, so if it isn't working then there would be no spark, again it would be a longshot but not a no shot, lol.