The car at times will not start. What could most likely be the problem?

I'll turn the key, the lights will come on but no noise. Then, when I turn the key again, the car starts fine. I had the battery tested, and came out normal. But, the first start after re-installing the batter, was a hesitated crank. Maybe half a second hesitation, instead of immediate, like normal. I was going to crawl under, and listen for noise from the starter. But, If I hear nothing happening, what else should I check? Thank you for your help. I hope to hear from you soon.