Why did I lose power of acceleration, while driving?

I was going 55 in my 2007 Nissan sentra, then, all of a sudden i lost power. The car stayed on but when I went to push the gas, the rpm nor the speed would move. So I put it in park then back in drive, had to hold pedal to floor to move ,max speed 2mph. Got to my driveway an it started accelerating normal

Don't know why, any suggestions???