Furnace short cycling is very hard on the furnace and hard on your energy bill. Furnace short cycling can be caused by (1) the thermostat anticipator (if equipped) not set high enough, (2) gas valve gas pressure set too high, (3) blower speed set too low or weak blower motor capacitor (4) duct work too small to provide enough air flow for the furnace, (5) evaporator coil stopped up with dirt or lint or (6) a furnace that is sized too large for your home. I hope this helps you find out why your furnace is cycling too much. I hope you have a blessed day!