In another narration of Tirmidhi, Rasulullah ￼ is reported to have said, ‘He who performs Fajr Salat with Jamaat and remains seated in the same place while engaging in Dhikr until after sunrise and thereafter performs 2 Rakaats Nafil Salat, (Ishraaq), he will obtain the Thawaab of one Hajj and one Umrah.’ (Tirmidhi).
From the above Ahaadith, we learn that the number of Rakaats to be performed are 2 or 4 Rakaats, and the Mustahabb method of performing it is to remain seated in your place of Salat after Fajr and engage in Dhikr, etc. until sunrise. Then, approximately, 10-15 minutes after sunrise perform 2-4 Rakaats. ‘If a person gets occupied in some worldly activity after the Fajr Salat, and after sunrise he offers Ishraaq Salat, this will also be permissible although the reward will be less.’
May Allah give us tawfiq to revive this sunnah, aameen