Putting car in reverse it started off on its own wothout my foot accelerating

This is usually caused by 'something' pushing on gas pedal.!!!!.. Oh yeah I know, there's no way that's it but just to be sure .. remove everything including the floor mat from drivers floor board and see if it happens again before saying that did not happen to you!

I own a Mazda 6 2009 and this is the third time my car got self accelerated when shift into reverse, it was so hard that I had to abruptly put in neutral to avoid a collision, genuine Mazda mats are tightly secured to the floor.....