I was once reading something about a band, punk band I believe, and the singer said that songwriting is like masturbation, "you have to sneak off into the corner and do it when no one is looking." While this is open for discussion, both meanings, the central point is true: you don't write songs in a group of people, or among distractions. Better said, you don't come up with good ideas with distractions around, you need quiet, control of your mind, time to think. Those nuggets of inspiration come at strange times, but not usually when there's something else to focus on, like a conversation, or playing sport. You have to be inside your mind, thinking, thinking about thinking, and feeling. Songs are, after all, emotions. We feel a certain emotion and then describe it with words and music, for others to experience, or share.
All songwriters have a list of ideas. It used to be scraps of paper everywhere but now we have notes in our phones. Sometimes concepts, sometimes just a line, and idea, sometimes a chorus with melody. Those ideas come to you when you're driving, alone and no radio, walking the dog, showering, all kind of random times. Sometimes you can really feel the emotion and scribble down a bunch of lines or descriptive words to help you later. Movies are good for me. It's something about being in the perspective of another character for 2 hours, another place or time, and comparing it to my own thoughts and life. I often get good ideas, usually when it finishes and I'm returning to my own world. Flying too. I get super inspired just sitting on a plane, and I have lots of solo time to just focus on one thing.
This is why I'm a slave to creativity at the moment. When I feel something, when I have something to work on, I have to put the time into it, because I don't know if it will end, if I will run out of ideas, if I will get bored with it, or if I will be too busy in the future to really focus like I am now. Plus I love to create.
Some people don't know how to quiet their minds. There's always some distraction, tv on, music playing, sometimes two or three things, it's crazy. When I'm driving alone I don't even turn the radio on, I'm just thinking, talking to myself, making plans, reviewing what happened, setting goals, just thinking about stuff. But I like to think, I think a lot of people are scared to find out what's in there.