Have Toyota Questions? Ask a Mechanic for Answers ASAP
The tires and wheels are the first thing to start with. Have the steering rack checked for freeplay in the inner and outer tie rod ends. Make sure the mounting braket/retainer bushings on the rack are not worn. As to how safe it is that depends on how bad it is. There is always a potential for something to break if the wheel shimmy is severe. I would limit your driving and have the suspension inspected.