Unexpected Mouse Activity

[EagledPar4]

Periodically, in fact frequently, while I'm typing a mail on Outlook (my office webmail) or using Chrome, when I move my mouse, a large arrow appear on the left side of the screen and closes the page I'm on. This causes me to lose the e-mail I am writing and it is unrecoverable. I thought this was related to the use of Microsoft Outlook on a MAC, but when the same strange activity occurred with page closings in Chrome I knew it wasn't a Microsoft problem. Apple support has no clue and says they can't help me. Microsofte had no clue either. I'm hoping this has happened to someone here on the forum and they have a solution for me.

Thanks