Assalamualaikum brother. In this verse "So woe to those who pray. [But] are heedless of their prayer – Those who make show [of their deeds]. And withhold [simple] assistance." [Quran 107: 1-7] is it only referring to those who pray just for 'show' or also those who struggle to concentrate during prayer? / sometimes I become overwhelmed with emotion during prayer and I'm not sure why and It affects it do you have any advice for this? May Allah bless you.
Alaikumassalam wa rahmatullah,
It is referring to those who pray for show without their heart being in it. The context makes it clear that all the verses together refer to the same type of person.
As for having difficulty paying attention when you sincerely want to, that is a different matter. Please see this previous answer on how to focus better when praying: How to focus better when praying (performing salah)