What might you mean by "flicker"? Is it dark out when the headlights are on and they're flickering? Or is there some daylight still out and the headlights go off and on?
If the latter, that would be normal. The sensor is in there at the top front of the dashboard so it probably isn't registering enough light as you drive in shadows or darkened areas so the headlights will come on...then once you hit enough light again, they turn off. I've driven through areas that are heavily tree lined in the middle of the afternoon and it will be enough to trip the headlights. Then I get back into a sunny area and they go off.
But, if it's the former...well...someone else will have to chime in.