In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
1- Tahajjud is defined as the late night prayer that you do sometime later at night after you wake up from sleep.
With regard to the best time for tahajjud, watch this video to know the detailed answer given by Sheikh Yaser Birjas, the Head of Islamic Law and Theory Department at Al-Maghrib Institute:
Almighty Allah knows best.
Source: Faith IQ