P1800E Overheating?

Hello, I recently bought a 1970 P1800E. The car seems to run at quite a high temperature most of the time, mostly just under the red. The temperature decreases when cruising but then goes back up at slower speeds. The gauge itself seems to stay low and then jump pretty rapidly but never really goes higher than just inside the red. Could anyone tell me if this is a normal operating temperature?! And if not, has anybody any thoughts on why this is happening or has any suggestions to solving it?? Any help on this would be much appreciated, Many thanks,,:)