86 D21 pu intermit. starting problem

My truck, sometimes, will not crank. Starter switch on and starter relay clicks but won't engage the solenoid until you turn the switch on and off several times and then everything is fine. replaced the switch, starter and solenoid recently.
The truck will do fine for weeks and then this problem occurs............any ideas ???

the wire to the starter

the battery

the ground to the battery

thanks for the reply. After posting I actually replaced the wire from the switch all of the way back to the starter and haven't had a problem since.