Lunging while driving all of a sudden

it all of a sudden lunges while driving in the city or freeway. it is like it cuts out (like out of gas) then goes right. it does it repeatedly. If I give it gas it goes fine when I keep pedal on freeway study it will start lunging. in city it is very touchy, pretty much if you let up on the gas it will jerk and lunge. freeway driving it like it runs out of gas, only last for about five seconds then resumes normal. it is odd because it has no loss of power I can floor it and it will go until I try and keep it steady. i am miffed cause I have seen no other ones on forums that do this. it does not stall. please help anybody have a clue?