Blower turns on and off even though the unit is satisfied
Welcome to DIY!

The blower runs when the heat exchanger goes over a set temperature and turns off when it goes under it as I bet you already know. However, heat is still transferring from where the fire was burning so it can warm back up and turn back on for a minute or so. The blower doesn't care if your thermostat is satisfied or not as it goes by it's own temperature control to make sure the furnace doesn't get too hot. That is probably your issue.