I second Vic's advice on trying the Sunday Song Writer's Group.
For me, the idea is key; which is often related to the title. Once I have the idea, I can filter the information that word fit the song regarding lyrics and music.
Titles are not copyrighted, so you can browse lists of song titles and see what you think it would be about. It's probably best to start with a title for a song you don't know so you don't get "stuck" thinking about the original song.
Here is one method to try:
Start with an idea or title:
For example, "The Miracle Mom" as a starting title/idea
Then ask the questions: who, what, why where, how. In this case, make a profile about this person and see where it leads.
Who was this woman?
What is the miracle? What did she do or is going to do?
Why is she called a mom?
Where does she live, wear, occupation, background.....be creative
How did she get the title or name miracle mom? Who gave her the title? Was it someone who loved and admired her, or was it a put down and a derogatory comment?
.....Is she really a woman? Maybe she was the first man to ever give birth......Maybe someone is talking to their mom and saying. "The Miracle, Mom".....
play around with ideas and opposites.....If you don't like creating the character as rich, make them poor. If she is not beautiful, make her ugly. If she is not shy make her obnoxious.
The more real or fleshed out the idea and character is for you, the easier it will be to fill in the lyrics. Then you could think what genre music the character would express themselves in. For example, is she a biker mom that listens to Heavy Metal......or is was she (or he) born and raised on country music? etc.....
Next step for me, is to find the "hook" of the song.....what the singer would want to convey or tell the singee.
After that, develop the verses to tell the story of how or why the singer is sharing their message/the hook to the singee.
Consider setting some restrictions and limitations or parameters to getting started. That seems to be helpful to get something going more than a blank page.