Bonnie is sick

I have a 1996 pontic bonneville. The other day the engine light came on, and the car didn`t want to accelerate from a stop. I had a machanic take a look said it was my fuel injector. He put fuel injector cleaner in it and sent me on my way. Today I stopped at a intersection ( first time driving it since) the check guages lights and bells came on, and the car lost power, ( to accelerate) I got it pulled over, and shut the car off. Then turned it back on and it worked. It did the same thing on the way home from work tonight. I would like to know what I am facing beofre I take it in to a machanic. Help !