Periodically I go through nostalgia periods.
I cannot really predict when they come on, nor can I really say what triggers them. I think it is environmental factors: maybe a long set of dull days or a series of tasks which are merely hum drum or even just seeing something that takes me back.
For me, most of my nostalgia revolves around role playing games.
The old style for me, right? 1979-1984, the high days of AD&D (first edition, thank you very much, when TSR still actually existed) and Gamma World and Traveller. Simple games, run with dice and pens and paper and miniatures and a whole lot of imagination.
There was kind of a group I played with from time to time but really it was usually just myself and my best friend. Outside of running around in the woods, it was our next favorite activity. We would play, and paint, and dream, and play more. Our games were probably kind of silly to those that were "serious" players - we often bent the rules - but we had fun. They were relatively innocent games - these editions, especially D&D, were largely before (I think) a great deal more focus on the bad side of things came into play.
Now, when I find myself bored or frustrated, I will start to think on those times, which leads to wandering through E-Bay and looking at everything on sale. I start to remember, and then I start to build lists, thinking "Wow - would it be great to start collecting X or Y again". It will take root for a few days, then I will pull myself back down to reality: I need less, not more. I do not have the time to invest. And even if I did get them, I would most likely not play them but just read and enjoy like a novel.
And the nostalgia will get firmly tamped down, leaving the seemingly less exciting but much more real world on my doorstep, waiting with its duties and responsibilities and needs.
Notwithstanding, I still feel the call of adventure.