I would like to know what module would cause the engine to turn over but not st

Changed fuel filter.fuel pumps runs...been leaning towards a sensor.but who knows which one.it will run great for a few days,then wont start.the starter turns over. No engine light.it cut off while driving after missing.wouldnt start I tried to start it everyday for three days..started up third day.since it started and seems fine the mechanic doesnt know what to check. Almost acts like its not getting fire Thank you

Sounds like the crank/cam sensor signal is dropping out. If you have a scan tool with live data, check your rpm signal while cranking. If the computer can't "see" the engine turning, it will prevent spark and fuel from reaching the engine.