I agree with the above who state a good cleaning and a new FP spring. Another thought, I wonder if the wing safety might be rubbing against the striker, causing the issue, and re-positioning the safety before firing alleviates the issue?

Gene - On a Mauser, the firing pin spring is compressed when cocked, and pulling the trigger releases the firing pin forward. Heavier the spring, harder the impact. On a gun with a frame mounted firing pin, like say a newer model S&W, where the firing pin is hit with a hammer face, then yes, a stiffer firing pin spring might reduce the firing pins impact.

Larry