If your vehicle is showing steering wheel doesn't return to center after a turn, here are the most likely causes and the parts you'll need to fix each one.
The caster angle in your suspension geometry is what naturally forces the wheels straight after a turn, much like the front wheels of a shopping cart. If the alignment is knocked out of specification from a pothole or recent suspension work, the steering won't return properly.
The front struts pivot on upper bearings when you turn the steering wheel. If these bearings dry out, rust, or seize, they create friction that prevents the steering from centering itself.
Ball joints act as the pivot points for your front wheels. If they lose lubrication, get contaminated with dirt, or are installed improperly (pressed in crooked), they will bind up and cause stiff steering that fails to return to center.
Tie rods connect the steering rack to the wheels. Worn, dry, or damaged tie rod ends can bind, restricting the natural return of the steering wheel. This can also happen if new greasable tie rods are installed but not filled with grease.
If the steering rack preload adjustment is set too tight (a common mistake made when trying to fix loose steering), or if the rack is internally damaged, it will bind and prevent the wheel from returning to center.
The universal joints in the intermediate steering column shaft can rust and seize over time. This causes a stiff, notchy feeling every 90 degrees of steering wheel rotation and stops the wheel from returning.