97R50 intermittent failure to crank

[Anotherpath]

Hi guys, I'm new to this forum so bear with me a bit. My 97 with M/T has been acting very odd for about a week. It sometimes will not crank at all seemingly after having run and warmed up well. I've eliminated the clutch switc and, relays, the battery shows 13.8V after running, the charging system is putting out 14.5V at idle. I cleaned both battery terminals and tightened them back. This morning it was 12 degrees F outside and it started. It was a bit sluggish as you might expect but it did start and run fine. The only thing I have not been able to do due to the cold is check voltage at the solenoid plug on the starter. I don't know if the solenoid could be the culprit after it heats up from engine temp or not, but I'm leaning in that direction right now. Does anyone else have any better ideas or has had this problem themselves? I have about 126K on the odometer and it was a one owner when I got it.
Thanks guys for any input.