Update on this issue. Seems that Avast Anti-Virus by default (in some cases) enables the Debug Logging option and generate these logfiles.

To correct, go to Settings - General - Maintenance and note that the Enable Debug Logging checkbox is not enabled. Now toggle the chekcbox to ON and then OFF again. This should now reset the option and no longer create the logfiles each time Avast starts up. At least it did on my three workstations which were showing this problem. Hope it works for others too.

Thanks to Avast support for finding the source of this issue.