2000 Chevy Astro vehicle starting

When the vehicle refuses to start, are you saying it won't even crank, or it cranks good but won't start?

If it won't even crank, can you tell if there is a load on the battery, when you turn the key to crank? You could use a voltmeter across the battery posts, take a reading, have a helper turn the key to crank, take another reading. With the key in the crank position, the reading should drop a little.

When it refuses to crank, you could turn on the headlites, turn the key to crank, watch the lites. If they go out or almost out, it's usually the battery or cables. If the lites stay bright, when the key is turned and no starter action, there is an open circuit somewhere.

You could do some testing at the starter relay, when it refuses to crank.