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It is the small inducer (exhaust) fan that goes on and off, after the heat cycle is finished, then the printed circuit card is likely going bad... that is common failure mode however.
It is possible that you might be mistaking the main blower motor for the exhaust blower... it is more common that those do a few short cycles after the heat cycle is finished.
If you can tell me the brand and model number of your furnace, and about how old it is, I can look it up... the model number is ***** a tag inside the burner compartment, and less comonly in the blower compartment.
I could also use a clear well focused photo of the wiring diagram glued to the inside of the blower door panel, take it up close, in very good light, straight on, and very well focused... I will mark it up with trouble shooting instructions if you handy.
You can use the paper clip icon at the right end of the tool bar above to attach the photo here.
We can go from there.