Service lights keep coming up

I was driving home the other day and every light in the car came on. The door locks where locking and unlocking. We have cleaned the battery cables which seemed to stop all the problems, but now it is doing it again. We had to tighten the cable back up again and it started fine. Went to leave twenty minutes later and the whole car went black/dead. We got it running again, but we did check the battery and it was fine. The battery is only two years old barely and I have put a new alternator and starter in. Any suggestions?