If the crank sensor with the problem your check engine light would be on, More than likely you have a bad igntion switch, to verify next time it does not start look and see if the check engine light is on or not, if it is not on, then more than likely your electrical part of the ignition switch has failed.
David DeLeon, VW Master Technician, Ontario VW
If this is helpful please click accept so that I can continue to provide this service. Thank you. Feedback and/or bonus is greatly appreciated