[Bill V]

Well here's my 2 cents worth:

I have seen exactly the same symptoms caused by bad batteries on numerous occasions through the years - battery ok on cold starts, but fails (not even a click) after the vehicle is operated for a while and the battery's internal components have had a chance to expand. After a couple hours of cooling down, the engine starts. If you haven't had your battery tested yet, go ahead and get it done. What have you got to lose? Good luck!

Bill