When was the last time the furnace was serviced by a professional? It is getting old and is having trouble waking up.

It could be a number of things. It may be a bad relay on the control board, a bad thermocouple, the thermostat is becoming intermitten, or the high limit switch is tripping. Your best bet is to have a tech trouble shoot it for you. It would be good if you could recreate the problem while he is there.

That may be the case...servicing. It was serviced 2 yrs ago w/ same problem. It was better for awhile then started again. No new parts were installed. I think just a cleaning or adjustment of something (I forgot).

To be clear, it only does it at night when hasn't ran for awhile. Does not do it during day when warm and not needed. So, its like something is not getting over heated but UNder heated??

Thanks