Well, I do feel a bit of resistance when I turn the key, but I haven't paid enough attention to notice if that is different than it has ever felt or not. It does feel a bit sticky though.
I did initially think starter. However, the fact that the starter does not try to engage the flexplate when the van is in gear is making me think it's not in the starter. The N/S switch seems to be cutting off the signal from the ignition switch to the starter when it is supposed to. I would think if the solenoid on the starter was stuck on, it would do it regardless of the position of the N/S switch. The starter solenoid should not be getting any current when the key is just in the run position. Am I thinking along the right lines with all that?
The fact that it is not acting up at this moment makes it rather difficult to diagnose. The switch is cheap, and doesn't look like it will be hard to replace. I may just do that and see what time brings.