Sayyidah Aishah (may Allah be pleased with her) said: When dawn broke, the Messenger of Allah (peace and blessings be upon him) would pray two light rak'ahs, then he would lie down on his right side until the mu'adhdhin came.
(b) Malik bin Anas (may Allah have mercy on him) differed from them, saying that he (peace and blessings be upon him) would lie down after the witr.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4884