TEmperature Gauge

[DaShEr_]

Hi guys, I experienced a problem yesterday with my 95 Sentra
The engine is 97 and Chassis is 95.
When I was running on the highway I noticed that the temperature gauged went up almost to the Danger zone. and then It came down in a few seconds to the middle (which is normal). When it was hot I pull over the car and I checked oil, water and all stuff. but everything was normal. and I didn't feel the engine hot it was like all the time. What can it be? Can it damage the engine? How can I fix it.

Thanks