My sister complained of similar problems when she started getting into shooting her carry pistol regularly.
In addition to the advice about leaning foward in your shooting stance, I would advise also doing some stretches before shooting, as you would before any physical activity. And some stretching afterwards as part of a cool down.
NRA Life Member
"Had King Kong showed up in Texas, Frank Hamer would have taken him down with his Model 8 in .35 Remington...well, he was kind of big, so maybe his BAR"