At 50 – suddenly it startet to grow dark hair on me. Ive always been a hairless person (exept the usual places)
Its under the t-shirt on the arms - but some on my legs?
You forgot the question part.
The question I guess is why? Just a WAG answer, it’s not on your head anymore and is drifting down! 
Sorry, maybe I should know this without asking, but - do you inhabit a biologically male or female body?
CairoCarol raises a good point - since menopause I’ve hair drop off some places and start growing on others. Hormone changes can result in hair changes in bodies of all genders.