Mac Mini 2018 halts with horizontal flickering lines

Hi all

I have a Mini which I bought in summer 2019 (so probably is the late 2018 model).

In the last weeks, the computer often halts, and then shuts down by showing some horizontal colour-changing lines like the ones in the photos attached.

In the following pic and vid you see this happening upon boot time (I also got also a kernel panic message from the logs when I successfully booted following this issue but am not sure if it is relevant - attach it here also)

Here is the evidence :)

And here is the vid: https://youtu.be/oDrfu9MKxFU

Also, here is also a vid where I captured the issue, where the overall desktop froze, and then the flickering lines appeared before the unit was shut down by its own. https://youtu.be/M1Dnvkjlmc4

Any ideas what this could be and how I can check it?

Could it be high temperature? Or is it something with the VGA?

I have to say that I have upgraded also the RAM in the mini, but so far there were no problems.

Also I've sent the unit to service (for an issue with the LG screen not waking up), and they supposedly ran it for 24h but they did not find something.

Would appreciate any advice.