I agree with Mark about potential infection and meant to add on the end of my post to run Malwarebytes, I think the following link takes you straight to free version https://downloads.malwarebytes.org/file/mbam_current/
Unless you really want to pay, make sure you don't agree to any "pro" or "trials" or similar terms that try to get you to upgrade.
Some viruses try to fool or stop ant-virus scans/detections and can cause a battle.
I'm also wondering if you have accidentally gone into tablet mode instead of laptop/desktop mode - this has a left/right setting for drop down menus and maybe more tricks like that.
Hit the Windows and "A" key at same time to open action centre, at the bottom will be tablet mode button which toggles on or off (light colour when off (desktop/laptop), dark colour when on (tablet) - click outside the box to exit this menu. Tablet menu usually has the start menu icons on the screen instead of pop-up.