2 questions to start:
What type of HVAC system is it? Is this a heat pump, a gas furnace, or ?
Can you set the FAN switch on the thermostat to ON, thereby using the fan when the unit is not running? And if so, does the fan run continuously - or does the same problem occur?

[This message has been edited by rpxlpx (edited August 04, 2000).]

Motor may be on it's way out......or faulty fan relay.

It's a gas furnace and I have central air. I CAN move the switch on the thermostat so that only the fan is on and nothing else (no heat or air). The fan will STILL kick off and back on, sometimes more frequently than others. Thanx for your response.

I think HOLLYWOOD'S got it. Or the fan may have a faulty thermal cutoff.

Thanx...I'll give that a shot