<HTML>One reason might be the front brake disk, especially when you brake. This is easy to replace. The other reason might be bearings of your left wheels (front or rear). That will be more expensive, and you have to go to garage to replace it (about $150 can for each side). Good luck.</HTML>
<HTML>I suggest you go to garage and find the problem ASAP. If really the bearing is wrong, replace it immediately. Otherwise, next item will be the axle, at that time you will face much more than $150.</HTML>