What Causes Numbness In Ear And Neck?

my limbs have fallen aslleep at night before and I wake up, rub them unril I feel them again and then they feel normal. This just happened to my ear which ran down my neck to my little finger. They were numb...as soon as I woke up and sat up the blood flowed back down and everything felt normal. I am afraid to go back to sleep. Did I just sleep on my ear wrong or is there more to it?