The answer to 'my furnace keeps shutting off' is that there are several common causes, including a dirty air filter, faulty thermostat, issues with the pilot light or ignition system, or problems with the furnace's limit switch or blower motor. This can result in symptoms like the furnace turning on and off frequently, not blowing hot air, or not turning on at all.
For many of these issues, the solution may be as simple as replacing a dirty air filter or resetting the furnace's limit switch. However, more complex problems like a faulty thermostat or issues with the ignition system may require the expertise of a professional HVAC technician. It's generally best to call in a professional if you're unsure of the cause or don't feel comfortable troubleshooting the issue yourself.