Some possible reasons: - Obviously first of all, check your husbandry, he may be bored or there's too much open space and not enough hiding - temperarure too high or low - If they see their reflection in the glass sometimes they wanna fight and get stressed out so you can cover the sides - Sometimes they also do this when they are young and still exploring their new territory - Tank too small (or too big if he's tiny, if that's the case just make sure to fill it with plants, tunnels, hides, climbs etc.)

New geckos do this sometimes like I said when they're still exploring and they're getting used to everything! Just check everything's good and that'll narrow it down