I have been having very similar hot flashes since I was 37. Now I am 40. In addition, I have been having those hot flashes earlier than that age, before my monthly cycle. As I said, it tends to happen outside of the time period before my cycle and I am not certain what the reason is but I know it is linked to my exercise routine, which probably means that it is linked to my hormones.
Each time I participate in weightlifting and/or vigorous exercise, I get hot flashes that night and the following day.
I am not worried about it really.