Arduino resets when on wall power supply

Thank you for your kind reply.

The power supply was purchased a few years ago, I don't have an image or link for it.

Also I'm away so can't do any schematics.

I control a DC device with the relay but this happens when if no device is connected to the relay.

In the meantime regardless of the relay why does the board reset itself when RESET button is touched with a screwdriver?

Thank you.