If a new bulb doesn't fix the problem then the switch on the lamp is bad and lamp needs to be replaced. It probably has a standard E26 socket which means house voltage at the socket and the electronics are inside the bulb. I'm not sure what the lamp standard is but sometimes there is a switching circuit which provides a lower voltage to the user knob/switch for safety and uses that to control the house voltage to the bulb socket so there could be circuit board and componants at the switch going bad. Installing a new bulb will tell you where the problem is.