car problems it revs up by itself and then goes back to normal

first off I have a G6GT and I also have a bad muffler. Recently my car has been doing weird things. I get a message that says engine power reduced/service traction. The car also revs up by itself for a while and then goes back to normal. Saturday on the way back to work my car's engine disabled along with those other messages and after waiting for a few minutes I was able to start it. I think it might be a bad catalytic converter, but I do not know for sure. Do you possibly know what could be the problem?