Non motile gametes are produced during sexual reproduction in oogamy process.

Oogamy is a form of sexual reproduction. It is a form of anisogamy  in which the female gamete   is larger than the male gamete and is non-motile. The male gametes are highly motile  and are usually do of the travel necessary to bring the respective gametes together for the reproduction to initiate.

This process mainly happens in animals but can also be seen in certain algae , ferns and bryophytes.

Hope you find your answer