Why does radiator start to boil after only a few mins?

A radiator may start to boil after only a few minutes due to several factors, including low water levels, a malfunctioning thermostat, or trapped air in the system. Low water levels can cause the water to overheat and produce steam, leading to boiling. Additionally, if the thermostat is stuck or not functioning properly, it may not regulate the temperature effectively. Trapped air can create hot spots, leading to localized boiling as well.