why won't my starter engage on 2000 Dodge Ram Van 1500

turn the key and all the lights come on but starter does not engage. is it the ignition switch?? it works sometimes but less and less often.

Asked by for the 2000 Dodge Ram Van 1500
More likely a failed starter solenoid but I would fist check to see if the starter is getting voltage to the stater when the ignition key is turned to the starter position when the vehicle won't "turn over".