Fan. My fan takes about ten minutes to start turning once switched on. I can hear a whiring at the

Question

My fan takes about ten minutes to start turning once switched on. I can hear a whiring at the motor, but any assistance by moving the blade does not help.It is like a resistance which it has to overcome. It was OK when first bought but after 2 years developed this and is getting worse ie takes longer to start turning. Regards Deeno