Why am i getting up after 3/4 hrs of sleep, awake for sometime and then sleeping again. i am unable to sleep 8 hrs all through. is it a health concern?

Night time wake up: Lack of daylight is a stressor to most organisms and sleep may be a means of limiting exposure to this stress. The body responds by release of "stress" hormones like cortisol which rise through the night. Eating before bed, although commonly discouraged, is actually protective against stress/corticol rising as it provides needed "fuel" overnight. Having a glass of milk &/or OJ before bed can help.