Seem to happen more with warmer weather. Can't say for certain if humidity makes any diff. This is the update. I cleaned the neg bat cable this am. It is a clamp to the cable head type. I took it apart and cleaned the bare wires, post and cable clamp. There is a smaller gauge wire with the thick starter wire. Clamped them together. Started fine but now I have a battery/alt light that comes on above 1500 rpms. I figure change is good. I bought another clamp end - autozone is a block away from my office - to put on at lunch. I will clean the positive cable and post at that time. Anybody think alt could be doing something odd? I had the charging system checked last fall when it was giving issues and I changed the starter for the 3rd time.
Ok here is the update. I went to start at lunch and no go. I took apart the neg battery cable again 5 different way. As I touch the neg to post normally you get the alarm going off. Not here. Sometimes a weak try. Then I went to the pos cable. much crud. Cleaned it and used new cable head. Touched post and alarm goes off as it should. Car starts, alt light comes on for a second and off. 2 hours later car starts. Alt light still goes off under 1500 rpms. Mostly on with flicker when driving at highway speeds. I haven't had advance auto check the charging system again yet. Any direction would be a help.