Welcome to JustAnswer.com! My name is DriveFast71(Ron) and I will do my best to answer all of your questions completely and accurately.

When this light comes on, most commonly this is a sign of a failing alternator or battery. You can check this yourself with the use of a hand-held voltage reader. With the engine running, take a voltage reading at the battery terminals. If the voltage is not between 13.4-14.4v, or is fluctuation in and out of this range, the alternator will need to be replaced. If the alternator passes this test, shut the engine off, and let it sit for 15 minutes. With the engine off, take another voltage reading at the battery terminals. If the voltage is anything less than12v, the battery is not accepting a charge, and will need to be replaced.

If you do not have access to a voltage meter, most local "big chain" parts stores will run these tests for you, for Free, right in their parking lot.

It could be an intermittent fail. Or a loose connection at the battery or alternator. Check your battery cables and make sure they are tight. Check the electrical connector at the alternator as well. If these are tight, it's very possible for the alternator to be "on it's way out" and the next time that light comes on, I would suggest having the above tests done. .

Yes. At this point, unfortunately, you are going to need to wait until it gets worse/more frequent. Intermittent problems are the hardest to pinpoint.