Weird fault whilst driving? Help!

Driving home from work this evening and I experienced rather a weird fault. In lane 2 doing about 60-70mph, all of a sudden slight loss of power, then all back to normal again........However the temperature gauge stopped registering???? Anyone any ideas on why??? I pulled over as soon as I could, looked under the bonnet and expected to see an empty coolant bottle or some coolant type fault, but all appeared fine, nothing untoward??? drove home fine but the temp needle was not registering anything, all other electrics are fine????