There's a snatch of piano motif that surfaces from memory every so often. I know it's Mozart. I know it's from a CD or tape of Mozart recordings I owned before I retired physical media as a form of music librarianship. I'm thinking symphony 40 or 41, but it could also be a piano concerto, because I had a few recordings of selected Mozart works shorter than symphonic compositions. I know it's not the Requiem. I don't think it's from Die Zauberflöte.

Symphony 41: "Jupiter" in C major (K. 551)
... not here, although this was one of the symphonies I listened to probably hundreds of times on CD

The Great G Minor Symphony (#40) (K. 550)
The other Mozart symphony that I listened to, many many times on CD. Not here either.

There are 25 Mozart piano concertos. If I have to audit them, I'll do so in reverse order from #25. I have a feeling I puzzled over this once before, and if so, it turned out my mystery concerto was somewhere in the 11-19 range.

#25 (K. 503): nope
#24: nope. I think I'll recognize the opening bars, shouldn't take long.
#23 (K. 488): No.
#22 (K. 482): Oh hey, I recognize the beginning. Getting close. I don't think the piano bit I remember is in here, but I may have missed it.
#21: Nope, I don't even recognize the opening bars.
#20: Nah, this is lovely but it doesn't sound familiar
#19: nope
#18: