Here are the steps as discussed in the video to enable Ubuntu boot-time Grub boot menu and timeout:
Step 1:
$ sudo vim /etc/default/grub
Step 2:
Comment these lines and save the file:
#GRUB_HIDDEN_TIMEOUT=0
#GRUB_HIDDEN_TIMEOUT_QUIET=true
Step 3:
$ sudo update-grub
Step 4:
Reboot the system and test the Grub boot-loader menu.