I was having similar issues just last week when I was trying to install Ubuntu on my laptop. The problem in my case was that grub was not being installed properly.
I managed to fix it by using ubuntu boot repair https://help.ubuntu.com/community/Boot-Repair
run ubuntu boot repair from within the live CD and choose recommended repair. And that should fix your troubles. But every system is different and they all work differently.
Further more, if you are installing only Ubuntu on this system. Then I think it would be better to install in UEFI mode (change bios from Legacy mode to UEFI or something similar) rather than MBR. As that is alot more easier.
I installed ubuntu today again in UEFI mode and I chose something else when the installer prompted to erase disk or install ubuntu next to other OS. I created the following drives.
efi 200mb Efi drive
swap 16000mb Swap disk
ext4 733000mb root folder where ubuntu is installed "/"
after that everything has been working properly.