1995 Acura Legend gauge shows it overheating

I have an Acura 1995 model is Legend. The problem is such when you run the car it will go to hot on the guage then down to normal. It is now winter and it does it more then in the summer or it will persist on going to above normal the back to normal while driving in town however on the hiway it will stay at normal anyways the problem also makes the heater give cold air when it registers hot on the gauge then when it decides to jump to normal it gives out heat. I tried to replace the thermostat the problem still persist does it sound like a head gaskett. or something else?