Electrical Problem

Can anybody give me an idea where to look for a solution to this problem? My wife is driving home when the radio, A/C, power windows and wipers just stop working? Yet the car is still runing fine? She makes it home ok and when I get off work I check it out and find no problems. It happened a couple of times and never stays around very long. It did have a problem starting once, like it was a low battery. I have checked the battery for connection and cleanliness, all good. Should I be looking at the alternator or battery or another electrical component?

The problem is in the igition cylinder that you put the key in. A couple shakes and everything will turn back on.