Peripheral devices like USB flash drives, memory cards, and external hard disks can cause application functionality issues, even to Steam.
Try to pinpoint the time when you started experiencing issues with the Steam launcher. If you plugged a new device into your PC around the same time, that device could be your culprit (or maybe you have faulty USB ports).
Just detach anything you don’t need, restart your computer, and try to open the Steam app. In the case of required devices, try plugging them into different USB ports.