why after i drove my boxster for 30mins them tempature will at "0" of 180

[ferrari355]

i think my car is having problem now, after i drive it for around 30mins, the tempature gauge will point at 0 of the middle 180. sometime will at the next black mark which is the one before the 250'. i checked the coolant which is ok, also if i try to turn on the heater the temp will go up a little too. i think maybe the cooling fan is no working? anybody who had same problem please help me!!