Starter issues again!

Go over your wiring. Clean connections, verify good quality ground with the proper size wire. Voltage is only part of the equation, the stater need amperage. If the car sits, buy a battery tender. After going through 5 battery's over the last 20+ years of the car in and out of action (more out than in) I finally bought one and it nice to just disconnect it, connect the positive to the battery and start it up.

Have you tested the ignition switch?