Hi,

If the tree (you don't mention which kind of oak) is otherwise healthy, immature acorn shedding (abscission) is a normal process. The degree of acorn drop can be the result of one or more of many environmental factors.  The attached link offers a detailed explanation of the long process of acorn production :
https://ecosystems.psu.edu/research/centers/private-forests/news/acorns-a-fickle-crop

This article suggests that peak acorn production occurs in 4 year cycles for red oaks.

Keep an eye out for twigs dying back (Kermes scale) and leaves yellowing from an iron deficiency (chlorosis).

Mark