The fix depends on what's wrong. If you can turn the steering wheel and it takes some movement before the wheels start to respond, have a helper do that while you look for what's moving and what isn't. Some of the suspects are universal joints in the steering shaft, a loose steering gear, and excessive clearance between the gears in the rack and pinion assembly. There's four tie rod ends. Did you replace all of them? The car also had to be aligned and the mechanic would have performed an inspection first. Did he find anything worn or loose?