I have BRYANT 394GAW048100 furnace. It works fine. However, once heat cycle is over, fan stops and then in about 2 or so seconds, fan starts again and sops in about 2 seconds. The strange thing is that if I turn off the furnace for 8 or 10 hours and turn on, the fan turning on/off issue is resolved for several days and issue starts again. What could be the reason. How to fix this problem

Thanks
John19999