What could make a clicking noise.

My wifes Accord sometimes makes a clicking sound upon startup. Clicking sound seems to be coming from around the power steering pump area or the firewall on the passenger side. Sounds kind of like a selenoid clicking but doesn't appear to be coming from the engine like a valve or lifter issue. She says its getting louder and it usually clicks for about 5-10 seconds but she said today it clicked for about 30 or 40 seconds. It only happens once or twice a week either in the morning or when she starts up to come home from work in the afternoon.

Thanks