Homeowner informed me that the furnace fan shut off this morning. Also stated he keeps the fan on and there were no error codes on furnace. Upon arrival, I checked thermostat. Thermostat was on and fan/ac setting was on. Inspected furnace. Furnace fan was running as it should. Checked static pressure, checked amp draw from furnace blower motor. Checked error history on thermostat. Thermostat showed a system reboot at 7:14am and 7:21am. Explained to homeowner that thermostat will reboot when it is updating, causing fan and ac to shut off for a moment.