The exhaust vent for your furnace will be on the outside wall. Often bugs and debris can get in there restricting air flow. Could also be your thermocouple. Could be a lot of things actually but those are the easiest to diagnose. But sounds like it's not igniting. You may hear it click to try but the burner is usually a fairly audible flame. The fan turns on before ignition to blow out any residual gasses. It's doing that then trying to ignite but sounds like it's stopping there. The thermocouple senses the pilot and if there is no pilot it shuts down. Was it working before?