What is the engiine and year of the vehicle . Are yo getting an OBDII code. P0128? You can go to Advance Auto and they will read the code for free.
You can have a bubble in the system or a bad T-Stat.
You know, it could be that the system is operating perfectly correctly, and you just don’t have sufficient antifreeze. Have a mechanic check the antifreeze protection, and then the thermostat.
Check your belts for tension, they may be loose or bad and your coolant pump may be slipping. Happened to me already where I got the same alarm as you.