The answer to 'why is my HVAC system freezing up' is that there are several common causes, including low refrigerant levels, a dirty air filter, or a problem with the blower fan. Symptoms of a freezing HVAC system include ice buildup on the coils, reduced airflow, and the system not cooling effectively.
Some solutions you can try yourself include changing the air filter, clearing any debris around the outdoor unit, and ensuring the vents are not blocked. However, if the problem persists, it's best to call a professional HVAC technician to diagnose and repair the issue, as improper handling of refrigerant or electrical components can be dangerous.