iphone 3gs does not start

Sounds like a software issue to me. If it was working fine before you started seeing this behavior, it could be one of the apps you installed recently so some media you might have added to the phone.

Were to able to do a hard re-set and see if things cleared out? Press and hold the sleep/wake and home buttons simultaneously until the screen goes black and then release when the apple logo appears. If this does not fix it, try resetting the network settings - Settings>>General>>Reset>>Reset Network Settings.

From there on, your options in that order are to restore from a backup, and restore as a new phone.

Try Recovery mode...

1. Turn the device completely off and disconnect it from cable/dock.
2. Hold down the home button.
3. While holding down the home button connect to a computer with a cable (easiest) or dock.
4. Keep holding down the home button until you see a connect-to-itunes screen You are now in recovery mode.

How do you know that won't work? Have you tried? Paulcb has been around a long time and usually gives really good advice. Don't throw out ideas without trying them or you won't ever get it fixed.

Your best bet would be to make an appointment for the Genius Bar and have Apple take a look at it. They can run a diagnostic test on the phone to determine if it is a hardware issue. If it is and your phone is under warranty, they will replace it.

Since everything is failing in your case, I would call the iPhone support guys using this number - Germany (49) 01805 009 433

They probably will have some next steps for you.

Have you tried DFU mode to reinstall the OS on the iPhone? You can access DFU mode by doing the following. When in this mode the iPhone screen is black.
1. Connect the iPhone and your Mac
2. Shut down iTunes
3. Hold Power/Sleep until the red slider shows up, slide to shut the iPhone down. If this doesn't work hold Power/Sleep and Home until the iPhone shuts down.
3. Hold Start/Sleep and Home for 10 seconds (try to be accurate…)
4. Let go of Start/Sleep but keep holding Home until…
5. … iTunes starts up and finds an iPhone in restore/recovery mode. The iPhone screen is black.

Then you can reinstall the OS on the iPhone. Caution: This will erase everything on your iPhone.

This exact same thing has happened to me. Twice. I had to restore from DFU mode. The first time was from a backup, it happened again, and I had to restore it clean. So far so good (since last night). The first time I tried to restore, I got an error message, so keep trying. I got mine into DFU mode holding the sleep/wake button and home button at the same time while the phone was already plugged in. I counted to 10, and let go of the sleep/wake button, but kept holding the home button. Itunes recognized it in recovery mode after that and I was able to restore. Keep trying if it didn't work, it did take me a few tries the second time. Good luck!

Have you plugged it in to power for at least 30 minutes?

Is it jailbroken?

When I tried to restore my jailbroken phone from the phone itself it did that exact same thing, the Apple store was able to fix it. (never told them it was jailbroken)

That scared me out of jailbreaking for SURE.