1995 Nissan Maxima The Needle of the C-H goes up all the wa

Hi,

I have a question. The needle of the C-H goes up all the way when I drive the car for 5 or 10 minutes. It goes all the way up and then go down a little, then it goes back up to the H area again. When I check the coolant, I realize the coolant is low but then when I pour in the antifreeze/coolant, the problem still there. After I pour in the coolant, I go for a test drive. The needle still goes up all the way to H and goes back down little and goes up all the way again. It just doesn't stay at one place, it goes all the way up to H, then back down little and then back up again. Please help me out and tell me what I should do. Thanks

Kenneth