First thing that comes to mind is steering bearings/adjustment.
When you correct the turn; does it go right back to the same place or does it stay on the corrected path? (if so then bearing tension/wear)
Does it wobble back and forth constantly? (look at tire wear carefully)
If tire wear is even; does the tire have a single straight tread in the center? (this tread can wobble a bit due to road surface, especially in rain grooved pavement)
Past these answers you have to ask someone smarter.
