sir originally its a zoroastrian festival and mostly Muslims dont celebrate it though those from areas having proximity with Iran celebrate it and here in Pakistan some shias having roots in Iran do so and also carry on some rituals which are zoroastrian. some also keep fast.
but none the less Happy nowrooz to those who celebrate it
yes off course i didnt mean every muslim, but a significant number of muslims do celebrate it in countries like Iran, Afghanistan, Tajikistan, Samarqand, bukhara, Turkey, Kurdistan, Azarbaijan etc.
I have seen Shias do celebrate it, to be honest with you i dont know the reason behind it, as it has nothing to do with religion.