There is what is known as jalastul istiraha which is a sunnah. This is to sit for few seconds after the second prostration before standing to the second or fourth Rakah. This is a sunnah and the Prophet salla Allahu alaihi wa sallam used to do it. However, there is no raising of the hands in it.

I was at Jummah congregation yesterday and saw a man next to me whom during the sujud in the first rakah decided to sit for like 3 seconds and said Allahu Akbar while sitting for like 3 secs with raising his hands while saying the takbeer while still sitting down when all of us have stood up including the imam has even started reciting Fatiha for the second rakah. Is this sunnah?