Need help with grinding noises
 

Okay, so, during the recent cold snap i started my car every few hours. Yesterday i started it and it made a grinding noise and the engine revved up but same right back down. On my way to class it kept making the noise on and off and i thought it was just the high wind blowing under the car. On my way home i noticed the tach bouncing when this happened and the car would act like its dragging. When i let off the gas it stops. Im lost and praying its not the cvt tranny. Any ideas?