I've had a similar sounding problem. I would wake up in the morning and as soon as I tried to sit up, I'd feel dizzy and sometimes my vision would get fuzzy/dark for a moment. I recall one occassion where it seemed like I literally could not raise myself to sit up even though my limbs were not "asleep".
One morning I got up and tried to walk towards the kitchen. My balance was so messed up that I ran into the side of the hallway even though I thought I was walking straight.
On another day, I actually had to crawl down the hallway on my hands and knees. On that particular occassion, I got the feeling that the problem was that my blood wasn't circulating fast enough. So, I [crawled] to the kitchen and made a cup of coffee hoping that the caffeine would kick start my heart. As soon as I felt well enough to drive, I got myself down to the doctor!
At the health center, they ran me through a bunch of tests to check my blood pressure, sugar levels, my vision, did blood tests for iron, looked at my ears and checked my hearing.
The doctor said that the cause was not out and out obvious, but she thought that my blood pressure was a bit low. She asked me if I exercised and I told her that I was on the rowing team. Ding! Ding! Ding! She suspected that I was waking up with low blood pressure and that's why I was having the symptoms I did - especially when it came to sitting up or standing up. Get this, she advised me to drink a little more caffeine and eat a little more salt!! She said that I was one of the few people a doctor would actually recommend this to!
Of course, texas*princess, I don't claim that this is what is causing your difficulty - I'm not a doctor.
I would recommend that you see the doctor and let him/her do some tests. I doubt that there are any "special" tests you can request. The doctor is sure to run through the whole battery of basic "first step" tests. If nothing seems to be the cause, then they will consult with you to look into it further.
I hope you are feeling better soon!
.....Kelly