I have two SSDs in my system, one for Windows and one for Ubuntu (and one HDD for storage). Installation works fine, and I can use Ubuntu with no problems as long as my other drives aren't connected. When I plug back in my other drives and try to boot to Ubuntu it doesn't work. It freezes on the loading screen and usually the top of the screen also tears in a way. I've tried 18.04.1 and 18.10, both have the same problem. I tried to install Solus instead and that worked, but I'd prefer to use Ubuntu as that's what I know best (fairly new to using Linux overall).
I've also noticed that in my the Boot Menu in BIOS it adds 2-3 different Ubuntu options, and that only happens after I've plugged in my other drives after installation (before it's just 1).
Edit: So what seemed to be the problem was something with the NVIDIA drivers. Funny enough, if I clicked the power button when Ubuntu freezed during booting it went to sleep, and when I pressed it again to go back out of sleep I could log on and use my computer just fine. When I changed from the X.Org X server driver to nvidia-driver-390 (under "Additional Drivers" in "Software & Updates") it works just fine and boots up with no problems everytime.