Sounds like either a low coolant issue, or a thermostat that may be sticking open some. The temperature gauge in these cars is basically an idiot gauge. Within a certain range of operating temperature the controller just tells the gauge to set in the middle and not to move, in the meantime the engine temperature could’ve changed 25 degrees. When the temperature goes beyond preset limits then the controller tells the gauge to move to either hot or cold, depending on what the engine data is. Guess Ford doesn’t want to worry drivers over what they consider normal temperature excursions.