The answer to 'why is my soffit curling shingles' is that the soffit material is likely warping or deforming due to exposure to heat, moisture, or other environmental factors. Soffit curling can cause the shingles above it to become misaligned and potentially start peeling or lifting up.
Some common causes of soffit curling include improper installation, poor ventilation leading to heat buildup, water damage from leaks or high humidity, and age/deterioration of the soffit material. This can allow the shingles above to lose their seal and start curling or lifting at the edges.