The heat reaches desired setting. Then comes on again, you hear the gas on, then it blows warm air for only five to ten seconds and shuts down again. Keeps doing this while maintains set temperature but with these very short intervals.

What is the model number of the furnace?

Gas ON or FAN on? Fan coming ON is usually caused by the "fan off" setting being set too low. There is residual heat in the plenum and heat exchanger and it triggers the fan on switch. I will assume this is an older unit as newer ones typically don't do this. Let us know what you have.

Depending on the age of the unit, it's either a sensor or a fan control issue. Has it always done this or did this just start happening? Have you made any changes... such as thermostat?