Sounds like death wobble. Check all of your front suspension and steering. Look for loose/worn tie rod ends, ball joints, hub bearings, etc. Pay close attention to your trackbar ends, make sure they are tight and not worn. Make sure all the nuts/bolts are tight. If all that checks out go for an alignment and tire balance. That should cover what may be causing your issue. You can also do a search here and find numerous threads about death wobble and how to fix it.
Here are the results of one search.
Don't run out and buy a steering stabilizer thinking that will fix it. If your front suspension/alignment is good you should not have DW without it.
Silence is Golden, Duct tape comes in Many Colors.
Journeyman Polyphase Meterman IBEW Local 387
Work with enthusiasm as though you were working for the Lord rather than for man.
Siena Jeep Owner's