1991 Mazda 626

There are many variables at play here. Check the tire wear--is it uneven or choppy? Have you hit any curbs etc lately? The steering rack, tie rods, wheel bearing, and even cv joints can have an impact on this. Vehicle caster (an alignment angle) can do really wierd stuff if it's off too. You can jack up the front end and check for play by moving each tire horizontally and vertically. Although the principles are simple, the diagnostic work can be advance. As a safety issue, I'd get this looked at as soon as you can. Good luck