Why do I feel hesitant to message them even if I am confident?

So as you all know I used to be shy for years before due to bullying and all but I overcome that shyness at 23 in mid 2024 during 3rd sem of MBA. Now I can talk to any one. I initiated conversation with women in Cafes and all including foreign expat women in Central areas of our city Bangalore in India but when it comes to messaging some women on Instagram who were my classmates in MBA, i hesitate. Yeah 5 months ago during our last ever day of MBA, I did surprise Anshika who was my crush in 1st year and even complimented her and also talked with Suhani who used to be curious about me in 1st year as I didn't talk much but when it comes to messaging them, I chicken out. I also bumped into Suhani in Church Street area 4 months ago again and we talked properly. I am 25 now and would still be able to talk to them confidently if I met them in person again but idk why I feel nervous about messaging them despite being connected on Instagram with Anshika. I am also feel hesitant to send follow request to Suhani. Can you explain why it happens?