Yes, very easy to diagnose. My dad and sister have it from time to time, and it's typically nothing to worry about. But get it checked out just to make sure your blood pressure is all good. =) But I guarantee you that's all it is, a quick change in blood pressure when getting up too fast. Happens to a lot of us.
I agree, you need to be seen by your doctor and rule out any kind of medical problem. The most obvious one would be orthostatic hypotension, where your BP drops significantly with position changes (lying to sitting, sitting to standing, etc). It's pretty easy to diagnose.
Start with yiour family doctor and go from there. Update us when you can.
Love your username too! GO STEELERS!
It may be that your blood pressure isn't rising fast enough when you go from sitting to standing. You need to talk to your GP about this and go from there.