2005 Subaru Outback 3.0R L.L.Bean Wagon Driving on highway 65 MPH throttle disengages from working.

Driving on highway 65 MPH throttle disengages from operating engine, engine goes to idle, pushing on the throttle doesn't do anything. Need to pull over, put the car in Park and shut off the engine, wait about a minute and restart the engine. Everything is back to normal the throttle operates perfectly for a week or more, there is no set time for it to happen again. It has happened 4 times on the highway in the last 3 months until now it happen city driving at a red light. I had to go through the drill of shutting off the engine, etc. It has been working OK so far.