Today when I went to make a right turn at a stop sign, I released the brake and the car started going backwards (it felt like it was in neutral, though, and there was no hill). I put the car in park and the steering wheel was locked. Just before this happened, there was 2-3 rough shakes from the bottom of the car.
In case it matters, its been 5k since oil change (I was actually planning on doing it today).
Help

I'm no good at anything car related and I'm scared of taking it in somewhere and getting gyped. I'm going to ask the oil change place to check all my fluids I guess.