Get the battery checked, it may seem ok but may not give enough amps. You could test this out by getting a jump start (another car's battery using leads) If your car starts, it's the battery at fault. Good luck.
Similar problem experienced on more than one occasion, most suggestions are OK (apart from the comedian) The soelenoid was certainly the cause on one occasion, and on another 2 occasions it was the brushes in the starter motor being worn too low!. you can try tapping the staring motor with the handle of a hammer, then try to start it.