There is a very thin line between showing off (Riya‘) and not showing off. It all depends on one’s intention before, during and after his good deed. No one can deny the effect of the congregational atmosphere this is one of the reasons why many acts of worship have been prescribed to be performed in congregation.
Hence, one should always be keen to have good intentions and seek only Allah’s face with his good deeds. Make Du`aa‘ to Allah to protect him against showing-off.