When waking i see a black spider shape that's not really there. i've seen eye specialist and had mri of brain, all normal. what could b causing this?

Called 'Floaters': It's not a spider but a reflection of the changes to your vitreous humor in the eye that causes small linear shadows on the retina that the brain sees as hair-like or spidery, and it's benign. It just happens to be in your vision, so it's more apparent, especially against a lighter background. No spiders in the eyes! Thank Goodness!