Why is my steering wheel wobbling so hard and erratically?

What is your question?

As I drive around 60-90kph my steering wheel starts to wobble harshly in my hand as though the steering is at fault. I dare not drive it until I know what the possible cause could be. Friends say it's either the steering damper or worse yet, the steering box. Can anyone give some good advice please. Thank you for your time....Mark