Iphone 4S jailbroken stucked in respring logo
Put your iPhone in DFU Mode : 
1. Plug your device into your computer with a USB cable.
2. Turn off the device (if it does not turn off the traditional way, hold both power button and home button until it turns off).
3. Hold the Power button for 3 seconds.
4. Hold the Home and Power buttons for 10 seconds.
5. Release the Power button but keep holding the Home button.
6. After about 15 seconds you will be alerted by iTunes saying that it has detected a device in Recovery Mode.
Normally you should be able to install iOS again but there are a lot of chances that you will not be able to back up your data. Moreover, your iPhone will not be jailbroken anymore.