You might try changing the ignition module in the distributor.  I've
had modules that fail, then after a while, I can put them back in and
they work very well.  You should carry an extra module, anyway.

Just install the new one and keep the old one as an emergency backup.
If the problem goes away, you know that was the answer.

I had a similar problem with a Buick LeSabre, random failures to start,
never a problem once it was running.  It turned out to be a bad throttle
position sensor that did not show up on the diagnostics.  It would
periodically hang up and may have been made worse  by unintentional
depressing the accelerator before starting.  I am now very careful not to
touch the accelerator before a start attempt.