Problem starting dodge sprinter 2500

What is your question?

When turning the key in the ignition, the engine won't fire sometimes. it is turning over but intermittently the engine will fire. We thought this be caused from the engine being cold but this issue happens in the middle of the day too, after the vehicle has been running for a few hours. However, if the key is turned over and brought back to the off position, then immediately turned over a second time, the engine then turns over and the vehicle starts. What would cause this issue? Thank you in advance.