Is repentance obligatory if one experiences a feeling of wanting to leave Islam and return to disbelief, without knowing what the intention is or how to perform it?

Apostasy occurs with a firm intention to disbelieve. Mere thoughts and whispers of disbelief that a person dislikes are not considered apostasy; rather, they are excused, and repentance for them is not necessary. A Muslim should strive to combat these whispers and get rid of them.