Today I get a problem “suppose in linux, one pc restart momentarily.then how do u solved it?”
My suggestion regarding this issue is as follows,
it may occur because of many issue.
1. may be hardware problem.
2. may be OS problem
3. may be configuration problem of inittab file.
If the problem is with hardware then you have to fix the hardware.
If the problem is with the OS then install a fresh OS.
If you boot your OS at run level 6 then the pc will restart momentarily. You have to change the default run level. As your pc is also restarting momenterily, you must have to log in at single user mode to change the configuration at /etc/inittab .
In my next post I shall try to discuss to change the default run-level.
Any comments regarding these issue will be highly welcome.
Reza's Blog 
Todd Partridge said
Try talking to the people in the Gentoo or Ubuntu forums. A complete reinstall shouldn’t be necessary.