ANSWER:

You should pray witr and sleep and if you wake up for tahajjud then you should pray in even numbers and not repeat the witr as witr is prayed only once per night.

If I am not sure whether I will wake up for tahajjud, should I pray witr or leave it? Again if I pray witr and suddenly wake up in midnight and want to pray Tahajjud can I do that?

Prayer, Taraweeh, Tahajjud and Qiyam-ul-Layl |