Why is my 1998 Jeep Cherokees left front wheel bouncing when I go over 60mph?

What is your question?

When I go just north of 60MPH the left front wheel will gradually begin to bounce and get worse if I maintain that speed. It is nearly uncontrollable. If I'm on a newly paved road it won't begin until about 65 MPH. I definitely need new tires, but it has been getting worse over the past year. Would you recommend tires first, or a combination of tires and shocks?

What makes this problem better or worse?

Better when I drive below 60MPH.

How long has your 1998 Jeep Cherokee had this problem?

Year and half.