Hi
Pressing Ctrl by itself should not open Windows Search/Start or switch tabs. Since Ctrl + Esc opens Start, this looks like Windows may be detecting an extra key press or a program is remapping Ctrl.
Please press Win + Ctrl + O to open the On-Screen Keyboard, then click Ctrl with your mouse. If this does not trigger the problem, the issue is likely related to the physical keyboard, its driver, or keyboard software.
I also noticed Armoury Crate in your screenshot. Please temporarily close Armoury Crate and any keyboard/macro/remapping software, then test Ctrl again.
If it still happens, open Device Manager > Keyboards > right-click the keyboard > Uninstall device, then restart Windows so the driver is reinstalled.
There is a similar Microsoft Q&A case where reinstalling the keyboard driver resolved abnormal Ctrl/Windows-key behavior.
Please also tell me whether this happens with the left Ctrl, right Ctrl, or both, and whether clicking Ctrl on the On-Screen Keyboard causes the same behavior.