Intermittent A/C Blower fan

Cadillac devil concur 4.3 A/C composer engages radiator fan works the clutch also engages but the blower fan works intermittently it works for few hours than it quiets and than work again next it works for a few minutes than off it goes and come back again in few more minutes. At all time the compressor and the clutch is engaged. And the system is working but it is just the fan blower that quiets and comes back by it self