Similar age and situation but have started a couple of companies before. I spent some time thinking about ideas last week to keep the mind fresh. At first none of the ideas seemed worth anything, many "also rans".

Then I started to think about all the things that are broken at my current company or which are frustrating and why. Within a few hours I had a dozen solid ideas that could be more broadly applied.

If I wanted to start a company again at this stage (not ready for another couple of years at least) I would rank these ideas by ones I could start on the side at first, or which justified leaving my job. The ideas that could be started in my situation and met my passion + other factors I felt important would be the one I would actually work on.

In the meantime I'm saving my pennies, learning as much as possible and having a blast.