Boot with a live USB, select “Try before installing”, open a terminal with Ctrl+Alt+T and install boot-repair:

sudo add-apt-repository ppa:yannubuntu/boot-repair
sudo apt-get update
sudo apt-get install -y boot-repair && boot-repair

Then type boot-repair and a menu will appear:

Select the recommended option.

If your system boots normally after recommended repair great. If not post the link to the problems reported.

On some systems this annoyance can occur:

If this happens to you, visit the link for a solution.