There are a number of reasons why your car ignition may not be working correctly. It could also be issues with your key, battery, or starter as well. If your car stalls suddenly or doesn't start at all, your ignition line may have been severed or it could be a manufacturer defect.
Most of the time your warranty will cover ignition switches up to a certain year or mileage. It may also be a transponder key issue or a broken key that is too worn out to turn the ignition correctly.