Shut Off Ignition to Engage Park - Gear Shift Service?

Periodically, when driving, my car will give me a message on the dash “Shut off Ignition to Engage Park”. The gear shift will NOT shift out of drive and the car accelerates VERY slowly. I really have to rev the engine to pick up speed. Once the car is turned off and rests for a bit, the message disappears and the car behaves normally. I searched the web for answers. Apparently, I am not the only one with this issue but I cannot find ANY solution. HELP!!!!