I use scrum for everything I work on. Including personal projects. The main reason being for those times. I know I'll lose interest, life will get in the way, and eventually that spark of energy will come back as you mentioned.
However, when it does it's hard to know where to start... unless you had a project to go back to and see where you were in the project. At the very least I've found it helps remind me what features I did complete and which I didn't.
Also I'd recommend spending the first day or so poking around your code, reading your comments, even refactoring some of it. The reason you feel lost is both not knowing where to start and it feeling like someone else's code in some weird way. You just have to make it your own again.
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