What is the best course of action regarding thinking about death and not rejoicing in it while reading the Quran and Hadith?

It is not possible to be certain about this matter, but it could be from the whispers of the jinn companion (Qareen). For treatment, be diligent in reciting the remembrances (adhkar), associate with righteous people, and attend scholarly lessons and circles for memorizing and reciting the Qur’an with tajweed.