2003 Chevy Malibu Acceleration w/pushing gas pedal

Intermittent problem. Happens when engine is hot and have been driving off and on all day or for a long time. Idles high at 1500 rpm in drive, neutral idles at 2000 rpm, idles in park at 3000 rpm. Braking is very difficult because it feels as if Im pushing the accelerator while braking. When I let off the brake the car accelerates on its own without pushing gas pedal. Its goes all the way up to 50mph or higher without pushing gas at all. Driving on interstate today I didn't use gas pedal, it went up to 70mph and then dropped down to 55mph then went back up to 65 then down to 50 then up to 65 then down below 50. It does this very slowly and sometimes holds a speed as if in cruise control but cruise control is off.