Why Is My Steering Shaking Why Could My Steering Wheel Be Shaking?

Why could my steering wheel be shaking? - why is my steering shaking

I have a 1999 Buick Park Avenue with 65,000 miles on it that I, as a secondary vehicle. Today, I noticed the wheel was shaking when I drive at low speed. Do not shake during braking or speeds.Just high when I left the gas and the car slides. All ideas are welcome. :)