Toshiba laptop shuts down then starts again (tried everything)


Apr 27, 2012
Hi, I have a Toshiba satellite a300-276 model PSAGCE. The problem is that when it boots onto the OS (windows 7-32 bit) it shuts down. Ocasionnaly, I can enter the OS, but it gives an error right after and shuts down. After shuting down, the computer restarts. Interestingly, before booting into OS, none of this happens. I can enter safe mode and work normally with the computer without this issue. So it's not a hardware issue. Can someone please tell me what's wrong with my laptop? I have tried a different PSU and still the same issue.
An aditional detail : This only happens when i plug the a/c cable on the laptop. With the battery he doesn't shuts down.