Answered by: Alimah Nasima Umm Hamza
I’ve seen people get up and move spots for each prayer (eg sunnah in one spot, then move a few feet for fard). Why?
بِسْمِ اللهِ الرَّحْمنِ الرَّحِيْم
In the name of Allah, the Most Gracious, the Most Merciful
The congregation and imam should move to different places after the Salah. This makes it clear that the fard jama’ah has finished and that the people are praying their individual sunnah prayers.
It is mustahab for the imam to move to one side after the fard, to pray the sunnah. 
The Prophet (PBUH) said:
“The Imam should not pray in the place where he offered the obligatory prayer until he moves aside.”
Only Allah Knows Best
Answered By Alimah Nasima Umm Hamza
Checked and approved by Mufti Mohammed Tosir Miah
Darul Ifta Birmingham
 Al-Shurunbulali, Maraqi al-Falah, page 118-119
 Sunan Ibn Majah, Book 5, Hadith Number 1494