Ackack

I've had my car back from Tuffy for a few days now. I had to return my car 3 times because the rack and pinion they installed kept being faulty. Then my alternator goes bad while at the mechanic shop. They replaced the rack and pinion and alternator. Everything has been going smoothly until today. I was in the parking lot and started my car and it wouldnt turn over Radio, headlights, ac and all is turning on but not my engine. I kept trying again and again. I decided to make sure my A/C was off before I tried to turn my key again. The car then started with no hesitation. I drove back home parked my car. Turned my car off then on with no problems. My concern that this will happen again. Im guessing its a BAD ALTERNATOR, any ideas?