What is the nature of involuntary repetitive looking and glancing? Is it obsessive-compulsive disorder or demonic possession, and how can one get rid of it?

We advise you to fear Allah, to constantly recite the prescribed remembrance (dhikr) in the mornings and evenings, upon leaving and entering, and when sleeping and waking. Also, frequently seek refuge in Allah from Satan when you feel what you have described. We also advise you to make abundant supplication (du'a) and recite the Quran, bearing in mind that unrestrained looking and excessive gazing can lead to severe consequences. Allah has commanded lowering the gaze, as He says: "Tell the believing men to reduce [some] of their vision and guard their private parts. That is purer for them. Indeed, Allah is Acquainted with what they do. And tell the believing women to reduce [some] of their vision and guard their private parts." There is also no objection to consulting a trustworthy psychiatrist, as what has afflicted you might be due to the impact of the image you saw, and the Prophet, peace and blessings be upon him, commanded seeking treatment.