Occasional shutter delay with D3100

Hi all,

I'm experiencing an occasional shutter delay with my D3100. When i am taking a picture, i press the shutter button halfway so that the camera auto focuses, and it beeps to tell me that the subject is in focus, however, when i press the shutter button down further to click the pic, it doesn't take the pic at all, or sometimes it takes the pic after few seconds. To take the pic, i need to release the shutter and re-focus. It is also causing delay when i have the camera in multiple shots mode, it is taking the shots very irregularly. By irregular, i mean it takes couple of pics and then stops and then again start to click. I m using sandisk extreme class 10 8 gb memory card. Do any of D3100 owners are also experiencing this issue? Is this normal, or should i be sending my camera back to Nikon Support for them to look into this? Please advise.

Thanks!