I would suggest checking all the wiring from the battery to the starter solenoid and the battery to earth. (car body) Also the small wire to the solenoid from the ignition switch. A poor connection may cause intermittent starting.

Are you saying it will crank and not start, or stops cranking?

Stopping cranking:
Is it a proximity key (buttonless entry, start/stop button)?
Perhaps replace the battery in the key?

Otherwise check wiring as previously suggested. Concentrate on earths. Underdone or worn/corroded earths can cause all sorts of electrical gremlins. Check battery connections too, corrosion on the connectors or a loose connector can stop all the power getting out of the battery.


Cranking fine, but not starting:
Check or even just replace the Crank Angle Sensor.
Usual fault with this is difficult hot start, but difficult to start in general can be this sensor. Without it, the computer cannot determine engine timing.

I had a very difficult to diagnose fault once. Starting the car when sitting for more than half an hour would take two or three attempts. But would then start and run fine.
Injector leak down was tested, so was fuel pressure in the rail and a flow test was conducted.
Eventual culprit turned out to be a split high pressure fuel hose inside the pump assembly.