My air conditioner is making a really weird 'stressed out' screeching sound on 2008 Nissan Sentra

There is also something "unhinged" inside the a/c box, I think. At first I could play with the button, turning it on and off, and the sounds would go away. The last time I turned it on, after about a week's rest, I got the screeching sound, which surprised me! I want to take to to the best place for repairs. Can you help me?

Asked by for the 2008 Nissan Sentra