Various solutions for autonomous retransmission on configured grant with respect to user equipment and network apparatus in mobile communications are described. An apparatus may start a first timer and a second timer when a transmission is performed on a hybrid automatic repeat request (HARQ) process configured for a configured grant. The apparatus may perform an autonomous retransmission using the configured grant when the second timer is expired. The apparatus may cancel restart of the first timer when the autonomous retransmission is performed. The apparatus may restart the second timer when the autonomous retransmission is performed. The apparatus may stop the second timer when the first timer expires. The apparatus may stop the second timer at the activation of a type 2 configured grant.