I don't get it...

so is my husband, always cold, at bedtime, he wraps himself like a mummy but sweats later on, he changes several times.

I have hypothyroidism, as does my 88-year-old Mom, which causes us to always be colder than what we "should" be. Maybe get her thyroid checked.

My 91 y/o mother is constantly hot & sweating, even in the middle of the winter. She refuses to put on a coat to go outside, even if it's 20 degrees. She keeps her apartment at the ALF like a freezer but is never 'comfortable', continuously changing the thermostat making it hotter/colder, etc. The moment she steps outside or in our car, she's unbearably hot and miserable. I should say she also has progressive dementia. Even in the old days when there was no dementia present, she was always hot & sweating.
Who knows? I try to ignore most of the temperature complaints, and just deal with whatever outing we're taking her on, etc.

In your other post you were concerned she may have UTI. Does she have a fever?

Dementia often places havoc with the internal thermostat. Aging changes our perceptions of temperature. Add dementia to old age, and temp perceptions can be all over the place!

I bought my husband Coy a cooling vest to enable him to play golf on moderate days. When he died I gave the vest to another gentleman who also had LBD, so that he could fish in the summer. And yet sometimes Coy would need sweatpants and a heavy blanket on a moderate day. I just tried to help him be comfortable in spite of his unpredictable heat reactions. (And I also kept him away from the house thermostat!) The rehab center that sponsored his golf league went around the course offering water frequently. Hydration is especially helpful.

MS is another disease known to impact heat sensitivity.

Whether we "get it" or not (I don't think medica science fully gets it yet), I think the best bet is to promote hydration and encourage comfortable clothes, even if they don't match the season!

As we age our skin, primary defense for body temperature, thins as we age. Feeling cold on even hot days are normal.

Low BP, low iron? I am cold natured. I will be bundled up shivering while others may be sweating. Dunno.
Maybe someone has a good answer and will come along soon.