2007 sometimes starts quick, sometimes 5 tries over 5 minuts

Sometimes its starts right away, then sometimes I hear it crank, and I can hold the key trying to start the car for like 30 seconds, and it just keep trying to start. Battery is new, spark plugs new, power never dips like in a bad or dead battery,
usually after maybe 5 times over 5 to 10 minutes it starts. Every time I take it to mechanic, they say no error codes are being reported, so i leave it with them, and they drive it, and say it starts every time. then I drive next day, and it wont start at some point during the day.