When central unit is turned on it blows hot air. Once it reaches it set temperature, cuts off and comes back on it blows cool air? What could be the problem?

Is the fan switch at the thermostat set to the "AUTO" position?

yes

How long is the furnace off after a heat cycle before the blower comes back on?

about 3 to 5 minutes, but sometimes it will come right back on

How old is the furnace? Do you by chance have a model number?

Not sure how old the furnace is, and I don't have a model number. I purchased the home 2 years ago and the unit was serviced then.

Is the brand listed on the furnace?

Can you see if it has a standing pilot? How long does the fan run before it shuts off,or does it ever shut off?

away from home at the moment so don't know the brand but i canhear a clicking sound before the pilot is lite

Well, I really need a little more info to go any further. Without knowing what type of furnace you have it is hard to know where to tell you to start. Most newer furnaces control the blower with a circut board. Older furnaces used a fan/limit switch.