I’m working on a 1981 280zx turbo for my first car but I can’t seem to get the starter to turn the engine over. I put a new Interstate battery in it and cleaned/checked all connections to ensure good contact. When I turn the key, the dashboard lights up and I hear one loud click but the starter doesn’t engage. After all of this, I removed the starter and took it to get tested. It turned out to be alright so I put it back in the car and it magically worked. After turning the engine a few times, it went back to the same loud click. Any ideas on what the issue is? Could it be the voltage regulator? Is it a bad relay? Thanks!