Car "locks up"; temp indicator; steering wheel.

I have a 2005 Chevy Impala whose temperature goes above the half-way mark when
it's parked or it's in idle, but that starts going down (but never back to the half-way
mark) when the car is in motion. If the car is in idle or or if it's stopped long enough,
it'll pass the the max temp line and start trembling and sort of lock up and it takes
about 30 seconds of driving for it to "unlock" and start driving smoothly again.
Yesterday was I stopped to make a turn, the steering wheel locked up really bad and I
had a very difficult time turning. A loud, screeching sound emanates from the engine.
The car doesn't have to be in idle or stopped for the temperature to rise rapidly and
pass the max temp mark. As soon as that loud screeching sound started, the car
doesn't "unlock" while driving. As soon as that max temp mark is passed, the car
locks up and stayed locked up no matter how long I'm driving (by locked up I mean
that the car is trembling and it takes longer for it to pick up speed). Any ideas?