“the job happens to be my all-time favorite”
What are you crazy?!?
I’ve had many jobs and I’ve liked few of them. If you have a job you love, why would you want to leave?
You don’t even have any plans. I’d understand this a little better if you had a project you’re dying to work on full time, but that’s not the case.
Why don’t you just keep your job and find a side project. If that side project gets big, go part time. If it gets so big, you’re “burning” to work on it full-time, then quit, but not before.
Good jobs are hard to come by and jobs you love are almost impossible to come by. Also, don’t discount all the data you get from your job to feed your startup plans. Lots of people would love to do a startup, but don’t know what to work on. People with jobs don’t have that problem as much. The job can be the source of lots of great ideas for things people actually need right now.
I’m the last person to discourage anyone from doing their thing, but job vs. startup is not a binary decision.
You can do both, at least for a while.
Keep that all-time favorite job for now. You can always leave later once something else has wings.