I'm new to this, I'm 43 and just realized I have Asperger's recently. I have a doc appointment to get tested in 2 months. I mention this only to say I don't know what I'm talking about except as it applies to me.
However, this has happened to me my whole life. I go through periods when everything is boring, nothing has any meaning, I can't find that interest or obsession. Then, when I find it, things are better for a little while, then I learn a certain amount about it and no longer care.
So I don't know if it's normal but it is for me, hope that helps a little.
Take care.
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"A feller wiser than myself once said, sometimes you eat the bear, and sometimes the bear, well, he eats you."
The Stranger - The Big Lebowski
Your neurodiverse (Aspie) score: 140 of 200
Your neurotypical (non-autistic) score: 59 of 200
You are very likely neurodiverse (Aspie)