Car won't start but starts again later

I'm guessing the engine had been run, as opposed to being cold, and when you went back to start it, there was no sound at all. That's a common occurrence when battery cables have a lot of corrosion on their connections; it's resistance that stops the electrical flow. And this can happen even with a good battery..... To fix this, first get a memory saver and connect it prior to removing battery cable connections. Remove cable connections at the battery and at the opposite ends and clean them.

Make sure batt. cables are tight .