MALE 67 Why Do I Experience A Hot Flushing From

MALE 67 Why do I experience a hot flushing from my neck up at all different times of the day.....other than while sleeping at night" It results in sweat running down my neck starting on my head. All my blood work is perfect. But this has been going on at least 3 months. It makes no difference whether I just ate or am just sitting or standing. It comes out of no where. It is very annoying.