Spieg16

I have a stock 1975 280Z with an automatic transmission. My car seems to have had this same problem for about 6 years now and I do not know what there is left to do to fix it. Sometimes when you turn the key the engine does not turn over at all then you turn it again and the engine will start right up. There have been times where I have had to turn the key 7 times to get the engine to crank. I have tried 3 different starters, so I know it is not that, also, a new battery, new alternator, and new voltage regulator, so it's not anything to do with the charging system, and my mechanic has also bypassed the neutral safety switch. I don't know what else to do. If you have any Ideas please respond, Jason