Mac crashes on startup!!??

I have a MacBook 2012 version and iv had it for a while. about 6 months ago I lost the charger and it the mac was dead and i never found a charger for a bout a month. I found a charger and got it back up and running again, this is when it started crashing when it would boot. the load bar gets like 75 percent done and then it dies. Iv done so much research and tried so many things in disk utility's but had no luck. After about 2 weeks I decided to try and boot it normally and it worked and i was using the mac normally for about a day until I decided to turn it off and the whole issue started again. Help would really be appreciated as i have tried so many options like trying to reinstall OS and the drive is locked and booting in single user mode, and nothing seems to work!