The RPM's are flaring and the lights are dimming. What's wrong with my car?

Your service engine light should be coming on...if so you might have a sensor going bad...some only malfunction when they become warm which would explain why it acts up less when not driven. If the light is not coming on it sounds like an alternator, battery problem...but that does not explain the rpm surge. I'm guessing a TPS ot ignition sensor. A big box auto parts store will give you a free scan if the light is on...but the information they give is often sketchy.