Ubuntu. Why grub don't loading?

Sometimes, actually when you have only Ubuntu installed on your computer, grub don't loading, that is when you turn on the computer, some time later loads ubuntu without showing grub. Issue can be resolve by boot-repair.

1. Add repository for boot-repair installing
sudo add-apt-repository ppa:yannubuntu/boot-repair

2. Update apt-get
sudo apt-get update

3. Install boot-repair
sudo apt-get install boot-repair

4. Run boot-repair

After these steps issue must dissapear.