Quick take
If cloudiness clears from the bottom upward, air is likely. Persistent suspended material points toward sediment testing and filtration; unexplained changes warrant a well-water test.
Rule out air first
Tiny air bubbles usually clear from the bottom upward in a glass. That does not require a filter.
Sediment and turbidity
Persistent particles can come from sand, silt, clay or disturbed well conditions. Multi-stage sediment filtration may be needed when particle sizes vary.
Iron can also create cloudiness
Dissolved iron may oxidize after pumping and form visible particles. In that case, an iron-treatment system is more appropriate than only using a fine cartridge.
Test after sudden changes
A sudden unexplained change in a private well should be investigated rather than masked with filtration alone.