I can't start a conversation

This may be weird but, I don't know how to start a conversation BUT I do know how to keep the conversation going.

As an example I often times play chess casually irl, while some of my peers are playing and telling jokes or just talking with their opponent I'm completely silent and don't really know what to say.

This also happens in other settings as in college I find myself pretty much silent unless someone starts the conversation, then I go from "shy" to "extroverted" just because someone started it.

And I genuinely try to start the conversation don't find anything to say other than "whats your name?", "how was your day?"

why would you say is that, and how can i fix it?