Restful sleep- A sub-type of Darśanāvaraṇīya (intuition-veiling) Karma;
1. The Udaya (rise) of this sub-type is responsible for comfortable sleep which terminates in happiness (or it ends easily).
nidrā - sukhaprabodhā svāpāvasthā.
(Sthā 9.14 Vṛ Pa 424)
2. To undertake sleep for getting rid of intoxication, fatigue, exhaustion (or weariness); it results in obscuring one's consciousness.
madakhedaklamavinodārthaḥ svāpo nidrā.
(TaVā8.7)
niyataṃ drāti avispaṣṭatayā gacchati caitanyaṃ yasyāṃ svāpāvasthāyāṃ sā nidrā.
(Kapra p. 9)