With neutral lock-off SW failure to start, we do not get a "click" at starter.Thank you for taking the time to respond, I'll look into that. While it's a 99, it only has 130k miles. I did try the neutral lock-off test, and that seemed to work in terms of it starting, and, I do shift into park rather gently because I'm in a very tight garage and just think "Oh, let's be careful while in this small space with this huge truck ..."
So try both shifting (1st) and tapping (2nd) each time it happens. Keep in mind shifting hard, does result in some vibration. Any vibration can move the starter contact, but usually takes direct steel to steel contact with starter. It can take a lot of vibration to move contact washer, so will not always work. Make sure when tapping on starter, you're not hitting plastic, rubber or wires. You'll come in between tubes of intake manifold, use a flashlight.
Here picture with intake off, to help know where to tap.
Intake manifold on the bench.