Idling problem when starting

buttomfly

Bought a 2004 grand cherokee with 109,000 miles on it three weeks ago. Everything worked fine and ran great at the dealers on a test drive. 3 days later would not start. Replaced battery, alternator and starter. Now it starts but
sometimes will not idle unless the gas pedal is pressed for a few minutes. Then it settles in and idles. Runs fine once it is moving. Worried this will only happen more frequently if I don't do something now. Problem? Throttle body sensor or dirty throttle body? Or something else. No error codes or engine light has come on.