Gas furnace
Keeps cycling on for 30 secs and it is not on -----the thermostat is not on- we are not using heating or a/c

The volunteer fireman part of me says...

Just as a safety item, turn the furnace off at the "emergency" switch or the circuit breaker box. I don't know what's going on but you don't need to deal with a fire.

What brand and model of furnace is it? Are the burners igniting, or just the draft inducer comes on, or just the blower comes on? Sounds to me like a fualty fan/limit switch, or thermostat, or control board. I suggest you have in a pro to locate problem,, and as medic suggested, shut power to furnace off until they get there. Good luck and please let us know what they find.