is there any application to restart the OS only
The "OS" (I assume you mean the launcher) starts itself up if killed, usually.
So, using a task killer widget (and making sure that "Sense UI" is NOT in the ignored list) might do the job for you.
I wanted to have a 'restart' application, instead of switching off and start again it seems better just to press restart (for me atleast ),
I tried your suggestion but didn't work
You mean sense? Get an app called force close widget, this adds a close button to notification bar, when no app is currently open in the foreground pressing this will restart sense.
Can I ask why you want to do this tho?
i think the thread starter want a 'Reboot' function. something like OFF the phone then turn it ON again.
I only want an app that will simply restart my phone instead of turning it off manually and then start again manually
Separate names with a comma.