While sleeping feel like i'm passing out so i wake up and wake up dizzy and light headed? only sometimes

Many reasons: Dizziness after sitting up in bed too quickly can be due to orthostatic hypotension if your resting BP is too low or you're dehydrated. Dizziness caused by sudden head turning might suggest BPPV. Make a log of the frequency, timing, duration of these events and take it to your physician. http://www.nlm.nih.gov/medlineplus/ency/article/003093.htm