In salah, as we were meant to stand for the 4th rakah after sujood, imam forgetfully sat instead of standing up. I noticed late and beat the imam to the pillar of standing but could have sat back down. I realised this later and made up my salah. Is this correct? What is the correct thing to do?

Ustadh AbdulAziz al-Haqqan

No this seems to me like waswas just follow the imam and say subhana Allah so that he stands up to remind him that he made a mistake. Do not repeat the salah.