1999 ram 2500, 5.9 diesel. turn key to start, just get a click from starter. batteries new. try a couple more times it

Welcome to JustAnswer.com! My name is DriveFast71(Ron) and I will do my best to answer all of your questions completely and accurately.

From what you are describing here, the 1-click and after repeated attempts it will start, it sounds very much like you have a faulty Starter Solenoid. On this vehicle, the solenoid is mounted to the starter, and the starter and solenoid are replaced as a unit.

Disconnect and isolate the negative cables of both batteries. Raise and support the vehicle. Pull back the protective rubber boot from the solenoid battery terminal far enough to access and remove the nut that secures the battery positive cable wire harness connector eyelet to the solenoid battery terminal stud. Remove the nut that secures the battery positive cable wire harness solenoid connector eyelet to the solenoid terminal stud. Remove the battery positive cable wire harness connector eyelets from the solenoid terminal studs.

While supporting the starter motor with one hand, use the other hand to remove the three screws that secure the starter motor to the flywheel housing.

Remove the starter motor from the engine compartment.

This may just be coincidental. The 1-click from the starter, and then starting after a few attempts is actually the classic sign of a failing solenoid. However, it wouldn't hurt to look at the Park/Neutral Safety switch as well. Check the electrical connector for any loose or broken wires. If the visual inspection checks ok, run a quick test on the starter: the next time it won't start, and you're getting the 1-click, lightly tap on the solenoid while someone cranks the engine. If it starts- replace starter/solenoid assembly.