There are 3 ways people write songs, generally speaking. Some begin with lyrics and a line may suggest a rhythm and/or melodic shape. Then, chords are chosen that support the melody. The chords generally contain some of the melody notes.
Others come up with a melody first and then, chords are chosen that support the melody. And then, lyrics are written to fit the melody.
And finally, others come up with a chord progression they like, and a melody emerges from the chord tones. And again, lyrics are written to fit the melody.
Some songwriters use a combination of all three methods.
Guitar players generally start with a chord progression or riff that serves as the catalyst for the rest of the song. It’s kind of the nature of the instrument. But I suggest you experiment with the other methods, too. It’ll expand your horizons and you may end up inventing new chords or voicings that support the melody.
And it’s always good to shake up your routine. Give it a try. A change in songwriting approach may lead to some interesting songs.
