Updates cause problem

[Kevin]

I checked updates last nite as I do most nites.
Last nites updates needed a reboot which i did.
Reboot went fine as usual.
Shut computer off as I do every nite.
Screen went blank - "no signal" -- normal.
However computer continued to run - drive blue lite stayed on - computer 
red lite flashed at 2 sec. intervals
-internal fan lite stayed on.
Only way to restart computer is hard reset button.

Ubuntu 18.04.03 64 bit
AMD Ryzen 5 2400G  with radeon vega graphics
16 Gb Ram

Where should I be looking for the problem?

-- 
Kevin

Ubuntu 18.04.3
Registered User