starts maybe?

2000 ford ranger it will start maybe drive it all day sometimes different places starts fine then it won't start turns over but nothing. hope you can help me,my dad has a 2000 ford ranger we've changed plugs,wire, coil, electric ignition switch and still does this---it will start maybe.drive it all day sometimes different places starts fine then it won't start turns over but nothing. it can sit in driveway and you can start it shut it off wait 5 minutes won't start after awhile starts. 3.0 automatic