One should have kavana (proper concentration) when praying Shemonah Esrei. If one is unable to have kavana for all of Shemonah Esrei one should make an extra effort to have kavana for the first Bracha (Magen Avraham). If one didn’t have kavana even in the first Bracha according to the strict law one is obligated to return to the beginning of Shemonah Esrei. However, nowadays if one did not have kavana one should not return to the beginning of Shemonah Esrei.
The footnote reads:
The Tur 101:1 writes that nowadays if one didn’t have kavana in the first Bracha of Shemonah Esrei one shouldn’t have to return to the beginning because once one didn’t have kavana the first time there’s no guarantee that one is going to be successful the next time. This is the ruling of the Rama 101:1.
My question is: Where there is a reason to think that the circumstances are that he will be able to concentrate better the second time (because whatever was disturbing him has stopped), is he permitted or even obliged to repeat if he did not have kavana in the first prayer?