Why would the front of a 1999 Chevy Tahoe sometimes start shaking while driving?
It could also be a slipped belt, meaning that there could be some inner damage to the tire. That particular problem usually shows up at low speed and can become a problem at high speed. The tire should be replaced if the belt is slipped. You will be charged for the amout of use you got from the tire, so if the tire is half worn out, you will be charged half the price of a new tire. Other possibilities are, bent rim or loose suspension parts, but start with the less expensive possibilities first.