At least I've also started coding, while mainly saving and continuing later, writing down my thoughts or stuff I'm planning later for adding, etc.
While motivation should be connected with fun-attributes, maybe either think of design / storyline / etc. as "chapters", working on the one that sounds awesome for this moment and let's get surprised how the game turns out?
Mine being mainly a concept that gets fused, parted, stopped still also published a while ago as prototype, then the platform wasn't hosting webgames (just mobile ones), one community didn't even reply and one declined mine because it's rather too focused on textlines than graphics. Recently I've still noticed this platform and published it, while inspiration came by a tribute of someone that gets the date fixed on the day I was releasing it.
In my case coding and releasing, same for the title, etc. being not just anything. It's how to get it perfect as I'm expecting it and being curious is other players even expecting a game like that being available. Probably those reasons could be motivating for keep on coding, or possibly if you find and get rid of bugs? Or the team-up with players could sound inspiring for either suiting with similar thoughts or receiving new ways of how to design visuals, audio or text there? Just thinking of where games could try to click for progressing in levels and exactly coding it with traps, so players have to find a more unique way ...would be just an option for a game that sounds not too common, nor hard to program, I guess?