Why do i get itchy only at night?

Difficult to say: Without a thorough history. You could be suffering from any number of issues from allergy to detergents you use for sheets, something causing irritation in your bedroom, certain medications like opioids, dirty vents in bedroom, anxiety, to bed bugs. Recommend seeing your primary to discuss thorough history and any skin lesions for further treatment plan.

Itching: Itching usually gets worse at night. You need an evaluation with an allergist. You don't mention a rash, so i assume you do not have a rash. Eczema is notorious to cause itching, so does scabies, if you do have a rash. The causes for your symptoms are many, you need to be evaluated.

Many things: 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.