What would cause someone to wake up randomly at night?

I am 21 years old, and for the last (I am guessing) 6 months, I have been waking up at random times at night...I am normally a heavy sleeper. I only get 5 to 6 hours of sleep on days that I work (at 4AM), and I get 8 to 10 hours on my days off (and that's not including the 3/4/5 times that I wake up at night). I also fall asleep at random times during the day (well not at work lol). I know I am not an insomniac cause I can fall asleep really fast. I rarely get Nightmares, I do get dreams about my pet peeves (like smoking for example...but that's like once or twice a month), but most of my dreams are "Wish Fulfillment Dreams"...so I would have no reason to wake up randomly. I have been losing a lot of sleep because of this, and it's annoying!!! I thought it would just pass, but 6 months later, it's still happening. Help please?