I can't move it at all. It's completely stuck and I try to turn it and it's like I'm going to break the key off. It happens once every 3 months or so.
My car has 100000 miles.
My car has an automatic transmission.
You have one of two different problems. Your key is worn too much and will not engage the tumblers enough to unlock the ignition lock cylinder. If the key is not worn out then your ignition lock cylinder is binding internally and would need replaced. I would recommend you have another key cut first to see if it fixes the problem for you. If that does not work, then contact a mechanic, like one from YourMechanic, to replace your ignition lock cylinder for you.