Sa this is an intermittent issue, that test is wildly insufficient for the alternator ground wire. If it is the cause (and not the ignition switch) if has failed under the red sleeve inside the crimp of the ring connector. The rocking of the engine makes the connection better, worse, non-existent, better, etc. at rest, resistance is probably fine. Idling it might be as well.

If the symptoms return, disconnect the wire at the alternator and give it a hefty tug...just do nt loose you balance and fall over when it lets loose.