I saw the thread title and knew it was you, Jerry!
My songs can come from anywhere...usually they're fragments and it's only later when I have time to piece together bits from days, weeks, months, years of scratching that a whole thing emerges.
Sometimes they come to me entire--the shower is a good place, and so is behind the wheel. Also just before waking up and just as I'm dozing off. I had one song come to me in a dream, where I was dancing around a kitchen with somebody's infant (not their "baby"), and singing at the tops of my lungs. I've written several gospel songs, and I'm not religious and don't know or listen to much gospel. I've written songs I can't sing, and ones I can't play, and I have NO idea where they come from (the future, when I *can* sing/play them???)
I have a hard time convincing people who ask that my songs do not come directly from my life, they do not always reflect truth or reality (though I like to think they sometimes demonstrate Truth or Reality) and that a lot of what happens in songwriting, for me, is mechanical--a rhythm or a rhyme often dictates the words I use, not the experience or inspiration from which I write.