lexus GS300 2006 steering wheel locked

Could be something wrong with your transmission

If it's locked solid then it sounds like the linkage did not disengage when the key was turned ... check your gear selector and make sure that's not locked too. With the key on ,, your foot on the brake ... jiggle the gear selector while gently moving the wheel back and forth

If when you turned off the car and the steering wheel was turned in some position, when the power assist shut down with the engine, it could have put pressure against the key cylinder, not allowing you to turn the key and making you think something was wrong. Try turning the steering wheel a little one way or the other while turning the key to take the pressure off the key cylinder.