Windows 10 wanted to restart my XPS due to some updates, said will do it during idle hours but I still restarted. Boots back , couldn't. Tried again, same. Removed all USB devices , HDMI monitor, mini display monitor , still no luck. Removed power cable & it starts.

Slowly and carefully added all back one by one. Working for now ...

Talk to dell, and replace the power supply and adaptor.
This means simething is wrong there, and it will bite you in the ass in the future.

@magicMirror Happens only when I get update. All is well once I do a reboot after everything is settled. No issues with accessories {usb, hdmi, mini display port or even sd card} or power.

I know I have a battery issue and dell wants me to replace it {will do}. The adapter is fine ,they said. Changed HDD as it was earlier faulty but not such problems with the new one