Accelerator Stuck problems of the 1997 Volkswagen Jetta

Accelerator sticks when in high rpm, if you hit the brake it slows the car down a little but the car continues to accelerate. This has happened 2 times when I'm going around 60pmh and have dropped into 4th gear to pass someone. I had to shut the car off to stop it from accelerating. Then when the car was shut off and in park and the emergency brake was up, I tried turning the car on and as soon as I turned it on it revved up really high. It finally turned on normally after in turned it on and off a couple times. The accelerator has also stuck when I was going around 70-75 and hit the accelerator to pass someone to get into a different lane, I did not drop into 4th gear, I was in 5th gear the whole time. This time I was in the middle of 5 lanes of traffic and didn't have the option to shut it off, I put the car in neutral and then shifted it back into 5th gear and that fixed it that time.