Hazrat Shaikh, Moulana Muhammad Zakariyya (rahmatullahi ‘alaih) once mentioned the following advice in a letter to a certain person who was experiencing bad dreams:
Scary dreams are from the side of Shaitaan. Therefore, to save yourself from them, you should ensure that you sleep in the state of wudhu, and also be particular regarding your clothing and your bed being clean and free of impurities.
Before sleeping, you should recite the mu’awwazatain (Surah Falaq and Surah Naas) together with Aayatul Kursi, and then blow into your hands and pass your hands over your body.
(Qutbul Aqtaab Hazrat Shaikhul Hadith Moulana Muhammad Zakariyya [rahmatullahi ‘alaih] pg. 427)
Source: Ihyaauddeen.co.za