If a old halogen lamp light is flickering it's either 1 of a few things;
A. The bulb is loose in it's socket, try a slight twist for older screw in bulbs
B. the bulb is about to burn out try a replacement bulb from another similar light if it continues
C. Something pulled on the cord to disconnect the wires to the socket or
D. Something damaged the plug and has disconnected the wires allowing power to flow
E. If has a Pull Chain, Quick Switch, of even a Switch running along the cord.
These switches can be worn out if overly used and can also create the flickering in a bulb
Most of these problems can be easily diagnosed, fixed or replaced
Now remember a fully functional lamps can be sold.