Car won't even crank...

My valiant did that for a couple of years. I thought I had a dead spot in the starter. I carried a foot long chisel and the once a month or so that it occurred I would jump the terminals at the starter and it would fire right up. One day, the chisel didn't work and I yanked the starter. The positive battery cable on the starter end had corroded on the inside of terminal and was now too big to make contact with the starter lug. The outside of the terminal was clean shiny metal and should have been good enough to make a reliable connection through the washer on the nut, but it caused an intermittant headache and taught me a nice lesson.