1987 Pont. Bonneville v-6

Help !
This car was in storage and has 20,000 miles on it. Occasionally will not start. Was towed to a GM garage. And started immediately off of the hook. The shop was perplexed and did nothing.
But this "fault" is continuous and without rational explantion.
Recently it just quit while driving. Started 10 minutes later.
As of 4-10. It simply will not fire.
We've found, over time, that cycling the shift handle seems to reset something. But this time. No 'at-home' tricks seem to work.
No apparent spark to the plugs (4-10). But why? What am I missing. And why the occasional restart without doing anything?
Note: it's a local driver only (thank God). But is now quickly becoming a large headache.
Any suggestions before I put it on the hook again?

Thanks --