Best Friend Wants to Date Me?!?!

I was recently broken up with and one of my closest friends, who is a mutual friend with my ex, just told me he wants to try us being an item. I never really thought about him that way but we’re very close, and I think he’s a great guy. He’s attractive, funny, smart, and I’m comfortable around him. I know his family really well, too. But I’m nervous for us to start dating and then things end badly or get weird. I just lost my best friend of five years because of us breaking up, and I don’t know if I could do it again. Any advice?