A device appears and disappears repeatedly in Device Manager

The repeated Device Manager refresh means Windows is continuously detecting and losing the device, so installing a driver during its appearance will not fix the disconnect. Unplug USB devices and hubs; if the flicker stops, reconnect directly to another port and use the device’s own power supply if available. From an elevated terminal, run pnputil /enum-devices /problem during the fault and record the problem code and instance. In Device Manager, record Hardware Ids and use View > Devices by connection to identify its parent. Install Windows updates and chipset, USB-controller, and affected-device drivers from Windows Update or the manufacturer. If a recent driver started this, use Properties > Driver > Roll Back Driver; otherwise uninstall the identified device, restart, and let Windows redetect it. Persistent behavior in a clean boot points toward the cable, port, power, firmware, or hardware, so test the device on another PC before replacing anything.