The next step is Dock Connector Assembly. Before even considering replacing it, clean it. Use a clean dry toothbrush to clean the Dock Port. See if this helps. If not, then with the toothbrush or a lint free cloth and some Isopropyll Alcohol, clean the Dock, especially the Pins which are on top of the mid rib. Let the Isopropyll Alcohol dry, 30 seconds to a minute. See if this helped. If not consider replacing the Dock Assembly. When you Restore again write down the exact Error Codes, because the ones you have listed, I have never heard of.
Thanks for your reply!
Since iTunes can see it only when it in Recovery/DFU mode, whenever I plugged my iPhone 4 into my MacBook Pro, an dialog popped up that told me iTunes has detected an iPhone 4 needing to restore. After I clicked the resotre button, the iTunes "status area" telling me "extract the software" something like that, and the screen of iPhone 4 flashed for one time (very bright white screen without text on it, and then going back to totally black), and finally the iTunes error dialog showed up with error code 2006.
I'll try the method you mentioned soon. Thanks!
USB Problem, possibly bad Cable.
I misread your original post "It keeps rebooting at every 10 min or so when It was plugged into my laptop".
I thought you had a boot loop problem, but you say "rebooting when plugged into laptop" this is not the typical boot loop problem, because you had the iPhone connected to laptop.
Connected by what, obvioulsy a USB Cable, Error 2006, is most often due to faulty USB Cable.
Clean that Dock Port Very Well especially with Isopropyll Alcohol, get a good USB Cable, try a different USB port on computer, or try a different computer.
Yes, it maybe a boot loop problem or other hardware problem. Since it will be a "dead body" without connecting to the laptop, the boot loop only happens when the phone was plugged into the computer.
I also tried different USB cables and USB ports on different laptops that I'm pretty sure they are all in good working condition.