Sometimes I Am Sitting At My Desk, In Air-conditioning, And

Sometimes i am sitting at my desk, in air-conditioning, and all of a sudden - like within sixty seconds - my body temperature just rises until i can feel the heat out of my shirt collar and i start to perspire usually my neck and head. Either i get up and walk around the cool office or stand beneath an AC vent and after another minute or two it goes.... no other symptoms but it happens maybe once every week... any time of day....