1997 Cadillac Deville Engine Dies and lights flash

I bought this used Caddy in Fall in 2006, has not givin me any problems until now, I started off with 82000 miles and am up to 113000. The car all of a sudden went dead and all the dash lights came on, the wheel didnt lock up but had to be turned to get off main road. I drove it the next day with no problem, and then took it on a 2 hour drive down a highway and did not have any problems until I got off onto a side road and up and died on me again. Mechanic did diagnostic scan and said it could be due to the corroded battery connection, they cleaned and tightened up posts, its been a week later and it did it again, but this time I didnt have to wait, I parked the caddy, turned the key over and it started right up with no check engine light, and its been over a day with no problems as of yet, please help, I would very much appreciate it