Starting

Sorry that I wasnt more in detail about no crank no start. Well, here is the whole story, this all happens intermittently, one time I started it and it died and would not start. Then tried it several times and then it started. Days later it would not start had batt. Checked 330 cranking amps tested bad batt, so I bought a new batt cleaned cable connectors and installed it. It was good for a week or so just like before then it would not start no crank no start. Lights would stay bright when ign was in start pos. Turn it off and on to start several times waited and it started. Then I was in a fast food drive thru and it died and the ign key was locked in the on position could not turn it off there were no inst lights nothing dead dead dead. Kept tuning off and on holding it on start position got out paid for my food walked back to my car put the food in and tried it and low and behold it started. When I got home I cleaned the body ground wire and it started 10 times in a row the next day my wife could not get it started, no crank no start. Now I have googled 2002 olds bravada no crank no start and this seems to be a normal problem with this vehicle series. Several people have had these same problems but no one, no one, could come up with the reason this happens. One guy spent about 800.00 to get it fixed at a chevy dealer I cant afford that. There were no reasons listed that would repair it. Surely someone has the answer. Can you help me?