Aurora R10, does not shut down Ubuntu 18.04

I have Alienware Aurora R10. I removed Windows and installed not supported by Dell Ubuntu 18.04. Everything was working fine and suddenly from 2 days the computer won’t shut down. Whenever I press shutdown it restarts. I tried every permutation in the bios disabling/enabling all available options . Deleted all recently installed programs on Ubuntu. Still I don’t see any result. Please help me with this issue