Problems with brand new iMac ......

So I bought the brand new iMac 21.5' in December and ever since I got it and I had to do an update, which required a reboot or just restarted it normal, it doesn't start. The apple logo loads up and then the circle starts spinning and spins for awhile, so i don't know after an update how long it takes for the mac to boot up versus a just normal reboot. Every time i turn off my mac it does and this and I have to go the disk menu ( holding command + R) which lets me reinstall a backup which is the only way for me to get my back to normal before my reboot and one time i chose reinstall mountain lion and then after getting my mac set up I restarted it and then it restarted perferectly fine and I kept doing it and it restarted normally. Then a couple weeks later I tried it again and it did the same thing It wouldnt start and just keep spinning!!!!

  • I can take it back to best buy since I have a warranty for 2 years if there is anything wrong with it and they cant fix it they will give me a new one
  • or what do i do ? Anything I can do fix it ....

p.s. Ive tried everything from repairing disk permissions to reinstall the os but nothing seems to be working....

any ideas of thoughts on this would really appreciate it