I'm a new Linux user and I'm facing an annoying problem with my customized grub boot-loader, suddenly after running the OS for a while -maybe two days or a week- my PC stack in keep repeating this screen which containing the manufacturer logo -sorry that i don't know it's name- and don't display the grub menu to choose between Ubuntu or windows but when I try to boot from my external hard drive that contain backups for the whole PC the grub menu appears and I can then boot the OS. this problem faced me about 6 times and what i do is recovering the nearest backup data but this cause me to loose all my new data. I always try to run the command ($sudo update-grub) but nothing changes. could you help me please? I'm still not familiar with Linux commands and consents so please give me some details.
GRUB_TIMEOUT_STYLE=menu
Default ishidden
.