With my lights on when the car lost power?

I have a 1999 mercury cougar with 111000 miles on it. It has an automatic transmission. I was driving about 65 mph the other night with my lights on when the car lost power, and the lights and everything went off for a few seconds and then everything came back on for a few seconds (including the windshield wipers which weren't on to begin with) and it kept going on and then going off. So I coasted to the side of the highway, put the car in park, turned off the key and then started it. It started right up so I drove it about 3 miles and it did the same thing again. It did this 3 times in the time it took me to get home which was about 6 miles. I haven't drove it since and that was 3 days ago. If my description doesn't make since its because i'm a female. Can someone help.