The key is identifying the source of the "Found malware" warning.
Could be some third party "crapware" that slipped in via some other software installation.
Does the notice provide any error messages, codes, links, or anything like that? An offer to sell a fix, some product to cleanout the malware? Figure you would mention that but need to ask anyway.
Barring some immediate way of finding the source you may have to stop as many applications as possible from starting up at boot time. Wait and see if the notices stop.
Begin adding back applications until the notice returns - that would be the offending application. Could be caused by an application that only runs at certain times: e.g., a backup or some application's routine attempt to phone home to report and update.
You can also use Task Manager and Performance Monitor to observe what all is running at any given time. Look for processes and services that do not correspond with what you are doing or otherwise seem to be unexplained.
Is there a common game or application on the tablet, laptop, and gaming PC? Any thing like that would narrow the possible culprits.
Could also be a false positive warning via Windows but I would expect that Windows would provide more information. But rather than being wrong, Windows is "just saying" sans any real information or explanation.