question #3 Sahih Muslim 755a, Book 6, Hadith 195 : How can one manage their prayer schedule if they are uncertain about waking up in the latter part of the night?

If anyone is afraid that he may not get up in the latter part of the night, he should observe Witr in the first part of it; and if anyone is eager to get up in the last part of it, he should observe Witr at the end of the night, for prayer at the end of the night is witnessed (by the angels) and that is preferable.