Hey lindog, Had the same issue a while back and was driving me crazy, was diagnosed with weak battery / corrosion on negative cable to be replaced / weak starter. I was in the same situation as you more than once, it was a nightmare.
Good news it was fixed with a simple DIY for me, it was a lose Positive terminal under the hood driver side. I detached it then cleaned it from debris and reinstalled it. Had no issues since then, and it starts much more faster than it was before.
Wish you all the luck.