When it fails to start can you hear the starter solenoid clicking? If you can hear a clicking sound and the starter won't crank the engine, you can narrow the problem down to a bad solenoid, starter wiring, or a bad starter motor.
If you don't hear a clicking sound when you press the starter button, then the problem is much more complicated. It could be a kickstand switch, ignition switch, wiring, etc.
Bookmarks