iphone 3g doesn't work after erasing all contents and settings

[astro89girl]

I've got an iphone 3g (firmware 2.2.1 and baseband 2.30.03). Last night I tried to erase all the contents and settings since I wanted to sell it. However, after an hour or so, the phone just went on and off, on and off. I thought it was part of the erasing process. So I left it till the next morning. To my shock, it was still the same in the morning. Help me how I can fix the phone please anyone...

I tried to connect it to iTunes, but it doesn't wanna read my phone.. Please help me.. Thksss