05' Outback with a 3.0L Engine

Car loses power and the RPMs go up. This happens just driving down the road.  
I shut the engine off, wait 10 seconds, start it back up, it runs fine. No rhyme or
reason when it's going to happen. I was told it was plugged catalytic converters.  
It seems if that where the case it would be constant. I hate to spend that kind of
money and still have the problem. When I say loses power I mean no power.