It is highly recommended to perform Nafila or Nawafil prayers. There is Nafila for every obligatory daily prayer. Nafila of Morning prayer is two Rak'ats before the obligatory prayer. Nafila of Dhuhr is eight Rak'ats (2 + 2 + 2 +2) before the obligatory prayer. Nafila of Assr is also eight Rak'ats before the obligatory prayer same like Nafila of Dhuhr.
Nafila of Maghrib is two then two Rak'ats after the obligatory prayer.
Nafila of Isha is two Rak'ats in sitting position or one Rak'at in standing position, after performing the Isha prayer.
Night Prayer (Namaz e Shab or Salat Al-Layl) is highly recommended every night which is either 11 Rak'ats ( the complete form) or two Rak'ats of Shaf' then one Rak'at of Witr which is the short form, or at least one Rak'at of Witr which the shortest form.
We can anytime pray any two Rak'ats of recommended prayer for thanking Allah or for seeking forgiveness or just for the sake of Allah.