Forester accelerating without touching gas

Tonight I went outside to move my Subaru Forester (1999 automatic 128k miles) into the garage. With my foot on the brake, I placed it in reverse. As I let up on the brake it started to accelerate quickly before touching the gas pedal. I hit the brakes, put it in drive and the car started to move quickly forward before touching the gas pedal. It’s normal for the car to coast slowly before touching the gas, but this is different - much quicker. Any ideas what the cause is? Thanks for any advise.

What’s the temperature in your area? Cold weather will make the engine run at a higher rpm when first started, and if you put it in gear right away the car will move more quickly than it would at normal idle speed after the engine has warmed up.

If this doesn’t happen tomorrow, I think you can stop worrying about it. If it continues to happen, have a mechanic look at it. The engine should not rev up more than about 2,000 rpm, even when cold. If it revs more than that, something is wrong.

probably just the throttle position sensor can be reading slight throttle