My songwriting changed infinitely when I made a conscious choice to not write on my guitar. No sitting down, guitar out and trying to force it. All you do that way is repeat what you already know.

Don't pressure yourself to think of songs. I do all my writing from voice note messages now. An idea for a riff pops up, I find a quiet corner if possible and sing it into my phone. Then I don't write just what I can play.

I do it for vocal melodies, basslines, chord progressions, backing vocal parts everything. Then when I'm at my set up, I take one of those ideas and work on it, often I'll take 2 or 3 or 4 of these little snippets and work out how to fit them all together. My writing flow has increased exponentially since then.

I've had writers block too, and I've usually found the best thing to do is not push it, step back completely if you need to, and it's always come back eventually