I am Makarand P from the Dell Social Media and Communities team,
With regards to your issue, i feel the problem could be due to a malware and i suggest you to run a full scan of Malware bytes anti-malware. This is freeware and can be downloaded from the following link
Also please check under Programs and Features for any toolbars or unwanted programs. Please uninstall the same.
Kindly revert for further clarifications,
Thanks and regards,
Dell Social Media and Responder