Cabin ventilator not working properly!

my cabin ventilator is working very strangely, some times it is blowing air and some times it does not, however, you can hear the noise of the ventilator even when it does not produce air. Its been happening for some time now, some times it starts working immediately and then it stops, or some times it starts working after 5 minutes or more, or never, but most of the time, it needs to be set on the lowest temperature on both sites and the AC must be turned on, Or the air won't start blowing at all.