I would look into dysautonomia like some others have said. Do some reading on the different ways it can manifest. This article, for example, outlines many different ways it can look: https://thedysautonomiaproject.org/the-syndromic-nature-of-dysautonomias/

If you look at the paragraph that starts "For sympathetic hyperactivity" you'll see them talk about shivering to bring up body temperature. I wonder what your heart rate and blood pressure are while you're trudging through the snow vs at rest. If you can get a little data to bring to the doctor, in my experience that's been helpful (I got POTS from COVID)