my 1999 S10 chevy truck has a severe vibration in the front end gets worse when going faster

Sounds like a belt broken in one of the front tires.

Your wheel(s) are out of balance. Check for mud rocks or other debris on the inside of the rim. Clean them. If that doesn't fix it check the tires as tuff4x4 has said. Also check to see if any wheel weights are missing?

Also check your Idler Arm, Pitman Arm, Ball Joints ! Good Luck & Let is know, ok?

Don't know where you live, but tire balance may be the issue. Also have the tire checked as stated above, a belt in the tire may be letting go. If the tire balance is fine and the tire is not the problem, as DeBo13 said, check the geometry of the front steering. If your in snow country, driving in cold weather and snow takes a toll on the vehicle, If your off roaden or just driving on dirt/gravel roads, your tires, balance or geometry is at risk. My guess would be the idler arm or ball joints if not the tires.