Front end shaking
You need to get into a shop right away. You have very worn front end part. This could be dangerous if a part lets loose.
"worn front end parts"
And also check warped rotors if felt when braking or wheel/tires need balancing and/or a belt in a tire is broken or even a cracked front subframe(a-frame), Like said already all the above is dangerous and needs attention ASAP.
Looking for a Used Suburban in your area?
CarGurus has 130 nationwide Suburban listings and the tools to find you a great deal.
Search GMC Suburban Questions
GMC Suburban Experts