I'm a bunch older than you. I've shot, a lot, for over 30 years. Every handgun you can imagine.
I get the EXACT same trembling when shooting a Kahr PM9. After about 100 rounds, my hands are literally vibrating. I have no idea why. But, it happens every time I shoot that Kahr.
It doesn't happen with revolvers or any other DA gun I have. I think there is something about the size of the gun, along with its recoil and the particular reach of the trigger may cause some weird position in my hands and the muscles cramp up.
I have dainty little girl hands (really, 8 1/2 wedding band). They are fairly tough and strong though, so, I don't think its a strength issue, just the size.
Anyway, unless I plan on getting into a protracted gunfight and all I have is my Kahr, its a non issue. When you get to about 75 rounds, stop shooting it for the day.