The Messenger of Allah ﷺ said, "When one of you rises to pray during the night, let him begin with two short rakahs."
حدثنا محمد بن سلمة عن هشام عن محمد
قال رسول الله ﷺ إذا قام أحدكم يصلي بالليل فليبدأ بركعتين خفيفتين
Its isnad is sahih. Muslim narrated it in 1:214, and Abu Dawud in 1323 / 1:508 of Awn al-Mabud, both of them through the route of Hisham bin Hassan, with this same isnad.