cruising w/o cruise control issue

[mankypurple]

My 08 yaris, automatic is having an issue. Every now and then it starts driving by itself. The cool light will come on and it will accelerate without my foot on the pedal. If I pop it in neutral it starts rev hunting bad. Or it idles really low and vibrates the car. I was thinking the pedal position sensor or throttle sensor might be to blame, but than again ive always owned manual minI coopers. This is my wifes car. I'm a little lost with its workings. Please help. Any advice is greatly appreciated.