Take it to your local Toyota dealer!
Possibly is carbon or crud buildup on the throttle body, lack of lubrication in the throttle cable, or the pedal physically catching on something on the floormat or carpet. I'd start with the carpet because it is easiest to check.
If you pop the hood, you'll see a tube going from the airbox to the throttle body. If you pull that tube off the throttle body, you can see the throttle butterfly, and if the area around it is dirty looking, cleaning it may fix the sticking. You can buy carb/choke/throttle body cleaner from any parts store, which will break that stuff up, and maybe a toothbrush for the tough stuff. It is best to remove the throttle body so that the crud doesn't enter the intake.