Q- Is it established from authentic Hadith that Nabi (sallallahu ‘alayhi wa sallam) predicted that problems and calamities would come at very fast rate for a person who combs hair while standing?
The Muhaddithun have declared this narration a fabrication. The narration is therefore not suitable to quote. (Talkhisu Kitabil Mawdu’at, Hadith: 710 and Tanzihush Shari’ah, 2 pg. 269).
Sharia’h has not stipulated any specific correct or incorrect method of combing the hair. Likewise, there is no restriction in either sitting or standing whilst combing the hair.
And Allah Ta’ala Knows best.
https://hadithanswers.com/combing-the-hair-while-standing/
https://www.islamweb.net/en/fatwa/399412/the-prophet-did-not-prohibit-combing-while-standing
https://daruliftabirmingham.co.uk/home/combing-hair-while-standing/