You need three things: fuel, spark, and compression. With fuel, from personal experience, a clogged fuel filter will make a car hard to start, or deprive it of fuel. Of course, a fuel problem could be a fuel pump. A long shot is to check the fuses. I have heard of others doing all kinds of troubleshooting, to find out they had a blown fuse. It may be nice if you could pull the plugs and check their condition. It may give some clue. NGK plugs work great in Sentras. Other brands may not (Bosch did not work well in mine). Only time I had a hard time starting a car is when I flooded it. The gas washed the piston rings of oil, and I lost compression. I replaced my coil. That was not the problem. I was towed to the my mechanic, and he put a little oil in each cylinder to increase compression and it started up. Not that this is your problem or solution, just something to be aware of.
My Haynes manual gives a few troubleshooting tips for the engine hard to start when warm:
-Air Filter Clogged
-Corroded Battery connections, especially ground
-Faulty Coolant Temperature Sensor
In addition to the above, it says if engine rotates, but will not start:
-Fuel tank empty (wouldn't that be funny!

)
-Leaking injectors, faulty fuel pump, pressure regulator, etc,
-Broken timing chain (would not think this, but maybe way out of time?)
-Worn, or incorrectly gapped spark plugs
-Broken, loose, or disconnected wiring in the starting circuit.
-Loose distributor is changing ignition timing
-Broken, loose, or disconnected wires at the ignition coil or faulty coil.
I think I would check for loose connections, check the air filter, fuses etc,. I have replaced my plug wires two times, but it just made it miss. Also, a bad injector would just make it miss in my experience. Since it was running OK, then stalled, I am leaning toward fuel/air starvation. Really wish you luck.