It's happened twice-once when hot and once stone cold. No solenoid click,dash lights all come on normal, battery voltage with a digital meter was 12.0 volts (not running). The 1st occurance (hot) it started normally after about 45 minutes. The second (cold) time was yesterday.
I jacked it up so I could get under it to check the starter. That was all yesterday. Today it starts just fine- all I did to it was put it up on jackstands. Battery voltage is fine when running- checked with a meter it was 14.5 volts. This happens without any pattern or warning.
Also when it wouldn't start I heard a relay in the glove box click, then another on the driver's clicked a few seconds later. Just telling everything I noticed. Any ideas?

have you checked the adjustment of the neutral safety switch? Just my 2 cents worth.
Good luck

battery voltage is low.

Your battery needs to be changed.

Make sure you charge up the new battery with an automatic battery charger before you install.

Good news-it's fixed. Double-checked my battery voltage-it was 12.42 engine off. Dropped the front drive shaft to get to the neutral safety swithc connector. It was difficult to get off- there was some sort of very sticky green-tinted clear goop on it (is this normal BlazerLT?). Anyway it checked out good. So I removed the starter and found that the plastic end of the solenoid where the terminal posts are was loose and would rotate about 10-20 degrees. Replaced it and now problem is solved. Thanks

green tinted clear goop sounds like grease to me.

Glad you fixed your problem.

Good for you for actually going out there and getting your hands dirty.