During a recent home inspection I found a furnace filter so plugged that it was causing the furnace to short cycle. This means air flow was impacted to the point that the furnace was overheating and the high limit was shutting off the gas to the burners.
Solution? Replace your furnace filters every 30 days during the heating season. It is easy and inexpensive.
If you're not sure how to change a furnace filter, this "how to" guide will help: