The Nissan Path

When I turn the ignition key on my VGE30 engine will fire up immediately, as expected. But now and then it won't crank. The lights go on, the shift lever is in P, everything looks fine but when the key is turned nothing happens. Not even a click or noise. It's like no current is sent to the cranker. I've been told that this behavior is "normal" to some WD21 vehicles (and even some newer ones) and it has to do with the selector/lever of the automatic transmission - it somehow would think the position isn't P or N and cuts off the energy to the cranker. I keep shuffling the lever back and forth and eventually the engine will crank and start as usual, as if nothing had happened.

Any clues?

Thanks.
Wagner