You can fix the every 2 minute restart problem after you decided to update your iPhone 3GS firmware to iOS 5.0.1 version. And simply follow the following steps and you don't need to throw your device into garbage can.
Fix iPhone 3GS Restarting Itself Every 2 Minutes After iOS 5.0.1 Update
- 1. Remove the SIM card from your device.
- 2. Navigate to Settings > General > Network, then enable 3G and Cellular Data (or toggle these if they are already enabled)
- 3. Insert the SIM card to your device again.
If it does not fix the problem, you can try another solution which is do a full restore and set it up to be a new iPhone. But do not forget to use custom firmware in order to maintain the baseband if you are relying on unlock.