A student has obvious symptoms of a disability which is relevant to the instructor's class. The student does not appear to be aware of the disability. The disability does make it harder for the student to succeed in their education. What should the instructor do to help the student?
Depending on the nature of the disability, I'd suggest first talking to the relevant disabilities/accommodation office. First, they may have some paperwork or data about the student which hasn't been given to you; I've had students with accommodations before who were simply uncomfortable or unable to present them to the instructor. Second, even if they don't, they'll have more guidance on what to do here which may be very school specific.