If you are referring to the temperature reading on the gauge, then it's possibly a bad thermostat.
It will also read 'cold' until the engine has sufficiently warmed up.
Lack of fluid (water and/or antifreeze) in the radiator.
Low engine temperature (bad thermostat).
Low coolant level.
Bad gauge.
Wiring issue.
Coolant temperature sensor bad or not correctly grounded.
Problem in an electornic control module.
StUck in open position
Thermostat is gone, change it
at the beginning it will be cold, but it will warm up as you start driving
The temperature gauge on a car fluctuates because the car's thermostat is opening and closing. The gauge goes up when the thermostat closes and the gauge goes down when the thermostat opens.
A signal from the temperature sensor on the engine.
Sounds like it could be a bad thermostat - not closing to allow engine to heat to normal operating temperature
If it is broken. It could be a faulty temperature blend door actuator.
Your car engine isn't getting up to the desired temperature, about 130 degrees Fahrenheit.
Low coolant level which causes an air pocket in the engine.
This is probably an indication that your thermostat is stuck open. Go to a radiator shop and ask them to test it.
It could be a pulley that is seized up on the a/c drive belt that's most likely the problem
Temperature gauge reads signals off the coolant temperature sensor. It can also point to a faulty thermostat. If your car runs rough in cold, idles rough and uses up more fuel then coolant temperature sensor is your problem. They are normaly a cheap and easy diy to do.