Indeed this is likely not a software issue, but it can also have multiple source causes. For the 2016 models, this is unfortunately a common problem.
In most cases, I would suggest possibly a failing GPU which likely means that Apple would have to replace the logic board, or a bad connection with the display port cable, and re-seating it could possibly help.
But from what I was able to gather from the official apple.com forum, is that many people have had this issue, some specifically say it would happen during cold weather.
No solutions found as far as a replaceable part that fails, they blame it on quality. I would take that with a grain of salt as someone might have the answer to the root cause of the horizontal lines issue on the 2016 retina 13” MBP.