This points to a likely mechanical issue rather than a camera setting problem. In general, there isn’t much safe user repair you can do inside a lens without risking more damage, so an authorized Nikon repair shop is the safest option.

That said, a few users with the same symptom found the front element had loosened and backed out slightly on its threads. If the front optical group is loose, autofocus can fail especially at longer focal lengths. Carefully check whether the front element feels loose. If it has backed out, gently snugging it back into place may restore focus. One report noted this must be tightened via the inner retaining ring using the small notches near the glass, not by twisting the outer barrel.

Use caution: don’t force anything or over-tighten, and stop if you’re unsure. If the element is not obviously loose, or tightening it doesn’t help, the lens likely needs professional service.