Q: MY iphone4 is switching on and off by itself in intervals. i tried restarting it and noting changed. Pls help me.

Hi there GKNAIR,

It sounds like your iPhone is restarting on its own. If it doesn't seem to be related to a specific app on your phone, then quit all the running apps, otherwise just quit the app that seems to be causing the issue:

Force an app to close in iOS
https://support.apple.com/en-us/HT201330

1. Press the Home button two times quickly. You'll see small previews of your recently used apps.
2. Swipe left to find the app you want to close.
3. Swipe up on the app's preview to close it.

 
When you have done that restart the device and test the issue again:

iOS: Turning off and on (restarting) and resetting
http://support.apple.com/en-us/HT201559
 
If the issue persists, backup your device to iTunes, then restore it as new and verify that it works. 
 
How to erase your iOS device and then set it up as a new device or restore it from backups
https://support.apple.com/en-us/HT204686

If it does, then restore your backup to either verify it still works and the software just needed reinstalled, or isolate the issue to the backup file itself. 

If nothing works, and the device keeps doing this even when restored as new, then you will need service for your iPhone:

https://www.apple.com/support/iphone/repair/

Thank you for using Apple Support Communities.