Engine not cranking over

I have a 2005 monte carlo with starting problems, the car has about 85k miles and has been well taken care of, when the problem first started it when I turned the key nothing would happen and I would have to turn the key back and forth 3 or 4 times before the car would start soon after that started sometimes when I turned on the turn signal it would make a a loud sound and the lights would all flash so I tried not to use the blinkers but it did not do it every time just sometimes and as soon as it starting making the sound I shut the blinker off, I took the car to a grarge and they could not find anythign wrong and it would not make the sound and it started every time with no problems after a few weeks the starting problem got worse if I drove the car for more then 30 - 45 mins the car would not start for a couple hours. I took it to a differant grage and the car did make th sound with the blinker and they think it has to something to do with the flashers the button fibrates when it is making the sound and the car would not start and they think it is the igntion there are 2 parts in the ignation and they cost a lot and they are nto sure that is really the problem so I brought the car home and my husband talked to a few people and they told him to replace the sencers and we did and it did not help at all, now the car is not wanting to start and one day it stalled when I was driving and the car would not start had to wait a hour before it would start and now the car does not want to start I stopped driving car about 5 weeks ago and sometimes even with it sitting it stills will not start most of the time any idea what is wrong, I have read a lot of people have this problem but can not find any posts with how to fix it thank you