Corolla / Matrix 2009-13 :: Loud Grinding Sound For Few Seconds When Starting The Car And High Initial Idling

I have the 1.8L engine with automatic transmission and when I start my car, it has a loud grinding sound that lasts about 3-5 seconds. The Initial rpm after you start the car also idles around 1800-2200 rpm for almost 10 seconds before it goes back to 1000rpm.

The high idling also stops if you shift it into Drive (D) or Reverse (R) but in Neutral (N) it will jump back up to the high idle.

This started occuring november of last year. At first I took it to dealership but they could not diagnose it because they never heard the sound. It ONLY happened when it was cold below 30 F, but recently it has been becoming MORE and MORE frequent and now almost happens everytime I start the car. But it won't happen if the outdoor temperature is above 60 degrees or if I start the car shortly after I shut the engine off (like a 2-3 hour break in between).

I thought it might be a loose flywheel, bad torque convertor, or a faulty electronic throttle control system. I do NOT think it is the starter because it starts everytime even on the coldest of days just that the grinding sound is annoying.