In Ubuntu based Distros the grub menu is normally hidden you can change that by editing the /etc/default/grub file.
when you open the file you will find a line that looks like this
Code:
GRUB_TIMEOUT_STYLE=hidden
Change it to this
the next line will be this
change it to this
That will give you 5 secs to make choices when the grub screen comes up If that is too short a time you can change the 5 to a 10.
Also you may need to change the font size do that by scrolling down the file and finding this line
or something smilar change it to look like this
Remember to remove the # tag or it will be ignored.
Save the file then issue this command in a terminals
The next time you boot grub should be visible.
You can also do the same thing via a program called grub-customizer via a GUI but I do not recommend using it because if things go wrong it is very difficult to revert the changes it makes to your system and if your not careful you can easily bork the system.
Good luck.