I had sweating and palpitations after having covid, it carried on for about two years and stress definitely set it off too, it finally calmed down but I still get symptoms occasionally. I’m also in my 70’s and my doctor assured me that it wasn’t uncommon for older women to have hot flashes even into their 80’s. I also did some research on this and it seems that it’s quite possible to get hot flashes into your 80’s, I found that it was much stronger after having a covid infection especially the heart palpitations.