Chosen Solution

Bought a refurbished iPhone SE. Works great, but sometimes the screen turns black and doesn’t work, although the backlight works. If the issue happens and someone calls, it rings and caller id appears in my smartband (fitbit charge 2), but the phone screen doesn’t turn on. This only happens when i lock it, if i´m using it this never happens. Usually when this happens i just press home and power button, restart it, and shake it or give it a bump and screen works again. ¿Should i check the cables? ¿Restore the phone?

If you can bump it and make the problem go away it’s most likely a loose video data cable. Opening it and reseating things should make it go away.