I have just seen that serotonin syndrome occurs usually within 24 hours. So far so good for me - I don’t have any symptoms yet.
I was reading this strange case about someone who got it after stopping prozac and then starting setraline (paroxetine) so that begs the question- how do you change medications if this happens:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2464814/