Do not user “vga=” parameter, it is deprecated. Edit /etc/default/grub, and uncomment:
GRUB_GFXMODE=640x480
Edit /etc/grub.d/00_header search for:
set gfxmode=${GRUB_GFXMODE}
on the next line, insert:
set gfxpayload=keep
verify that the new line is before insmod gfxterm
# update-grub2
# reboot