There's a fire starting in Adele's heart -- the singer is opening up on dating NBA super-agent Rich Paul ... saying it's the most "incredible, openhearted, and easiest" relationship she's ever been in.
The "Easy On Me" artist -- who started dating LeBron James' right-hand man this year -- detailed her new romance with Paul with Rolling Stone this week ... saying they first met on the dance floor at a mutual friend's birthday party years ago.