Will uveitis cause your vision to go in and out?

Yes. The vision will be affected during active inflammation. Lowered vision is sometimes the reason persons with some types of uveitis will finally seek help. Untreated uveitis can cause serious complications which can lead to permanent changes in the eye. You should be under the care of an ophthalmologist for this.
It can. This problem can only be solved by seeing your doctor and being evaluated face-to-face. After a thorough examination, your doctor should be able to tell you what's wrong and what to do about it.