I agree w/ bbforks, these trucks wind up with a series of partial opens in the wire harness connections that together add up to enough drain to prevent starter operation as it will not be able to provide quite enough current to completely pull in the starter solenoid. {does the starter run if you jumper directly to the wire connection that energises when the key switch is in the start position?}, but then gets intermittent (sometimes hear a click when in neutral, no click in gear, but starter does not turn, maybe hitting the starter, or moving the directional lever seems to fix it some, a jumper on the neutral switch may help for a while, and it has the same feel as just about like a bad/dirty battery post). This is usually worse in trucks that were LPS rated when new as the voltage drop in the LPS disconnect box is one of the worse culprits, but the key switch and neutral safety switches and their connectors are all part of the concern and usually about equal in the cause and effect.
The local Toyota dealer will try and sell a complete wire harness or replace the truck with a newer unit, as the 'correct/warranty-able' repair.