ʿAbdullah b. Mas'ūd - Allāh be pleased with him - said:

Falling asleep when remembering Allāh is from Shayṭān; if you want you can test this: when you lie down and want to fall asleep, try remembering Allāh 'azza wa jall.

Al-Bukhārī, Al-Adab Al-Mufrad. Graded ṣaḥīḥ by Shaykh Al-Albānī in Ṣaḥīḥ Al-Adab Al-Mufrad Vol. 1 p490.