i have not exactly pin pointed mine down but i would wager my money on exhaustion for me the more exhausted I am the more severe the numbness and or muscle pains i have and also the end of the day it appears to hit me

hope u get some good feed back on this cause i have been keeping mental notes on this since 2006 to see what triggers it and exhaustions seems to be my most common factor

might want to check into pinched nerve if it goes away when u move your arm or legs mine is with me pretty much always, joy joy