1998 K1500 Air Conditioning is intermittent

A/C sometimes blows cold and sometimes blows hot. Any suggestions what to check or troubleshoot to figure out why?
I drive it with AC on and cold, after it sits a while and then next time I start it might blow only hot air.
1998 K1500 pickup , 5.7L

Failed temperature control air-door actuator?

Failing compressor clutch?

Failing pressure switch?

Failing dash control unit?

When this was my Trailblazer, it was the compressor clutch.

Next time it is hot when supposed to be cold, pull over, pop hood, look and see if front of compressor is turning....probably not, then try to bump it somehow, either by slamming hood shut, or even use a rubber hammer- tap on front of compressor, if clutch engages, then you know you have a "too wide air gap issue" and the clutch driver need to be reset to about .020" gap. Very common issue.

Thanks, it'll be near 100F here for a few days so hope to see if it's the "too wide air gap issue" .
I've not heard of this. Can you provide a link to any reading on how to adjust.