Ubuntu Not Starting

So I have an ASUS FX503VD with a 1TB HDD + 128GB SSD. I have Ubuntu 18.04.3LTS dual-booted on it. But whenever I try to turn Ubuntu on, it would go to the Ubuntu screen(where the dots appear under Ubuntu), and then my laptop would switch off. Sometimes it would turn on after the 3rd or 4th try, but today it has been about 2 hrs and still not started. Sometimes connecting the charging cable would help and it would start, but even that is not working. Also, if Ubuntu doesn't start and my PC shuts down at the Ubuntu(dots appearing) screen, the next time I turn it on, an error like "Couldn't get disk at 0x8000000e" appears. After that, if I get lucky Ubuntu turns on, but it just isn't turning on today.

Thanks

Shamelessly copied from Couldn't get size: 0x800000000000000e

The errors seem to be related to an attempt to import UEFI keys for Secure Boot.

I was able to stop the errors simply by changing a setting in the BIOS from [Customized] to [Standard] for Secure Boot Mode. The Customized setting allows you to modify the secure boot keys manually. The Standard just sets the default keys. Note: This fixed my error even though I previously had Secure Boot [Disabled] in BIOS settings.

Security -> Secure Boot -> Secure Boot Mode -> [Standard]