Hey. Songwriting sure has many methods and ways, and it can be frustrating , but also very interesting to explore and find what works for you. I got some valuable tips to improve this journey (that has worked well for me) :

In music universities in composition they have students write only rhythm first, before putting on a single melody or harmony on it.

This does not directly apply to your question, but will help your songwriting big time.

Write out different rhythm patterns on paper BEFORE you touch your guitar to make sure you create music with your mind, and not your hands.
If you are unsure about notation, you can write simple dots.


Another useful tip you can do is to be clear on what you are writing for. It is usually a combination of these most common categories :

1 :Make people happy / being appreciated
2: God
3: Money
4: Self expression


Hope you find this useful