Recently, Samsung effectively acknowledged a battery issue with its Galaxy Note8 flagship. And now the company might be facing a problem with the Galaxy S8 and S8+ as some users report their units randomly wake up without being touched. Here's how an affected user explained the issue on Samsung's official forums: My new S8+ phone has started waking up from lock screen every 10 sec or so. I did factory reset but it did not fix the issue. This is really annoying. I did google search and it seems that others are also having similar problem. I tried to turn off everything in settings menu...
Source: https://www.gsmarena.com/some_samsung_galaxy_s8_s8_users_reporting_random_screen_wakeup_issue-news-28960.php