Hi I got the solution,
Previously, I was logged as user and placed systemd units in this location under /etc/systemd/systemctl, I’ve modified the location to ~/.config/systemd/user and used the following commands to enable and start the service.
$ systemctl --user enable heimdall.service
$ systemctl --user start heimdall.service
Now my pods are starting after reboot.
Reference Video :Managing Containers in Podman with Systemd Unit Files - YouTube