1988 Cadillac Seville What can I do

I had a shortage in the ignition wireing fixed a year ago by a drive way Mechanic he just cut the short out a replaced it with a new small wire. But the car will start up at first but if I go into the store an come out an try to start it it won't make asoundut it will not start, then after sitting for an hour or so it will start like a new car.I think my security system is acting up what can I do?