This sounds similar to the steering problem associated with the 2005 Malibu (others?) we used to own. It would periodically shut off, requiring a great deal more effort to turn the wheel. GM replaced the defective parts for free and extended the coverage for this defect to something like 150,000 miles. If they don't cover it now, hang onto your repair bill, it may become a covered repair in the future and GM would then reimburse you for those costs.