Restarting on its own while on the internet

Question

while on the internet twice in one day i got a message saying your computer will restart because there was an error something like that and it restarted on its own?

Answer 1

If you have more than one user account, you must be logged in as an administrator to carry out these instructions.
Launch the Console application in any of the following ways:
☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)
☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.
☞ Open LaunchPad. Click Utilities, then Console in the icon grid.
Select the most recent panic report (with a name that begins with "Kernel" and ends in ".panic") under the heading System Diagnostic Reports on the left. If you don't see that heading, select  
View ▹ Show Log List
from the menu bar. Post the entire contents of the report — the text, please, not a screenshot. In the interest of privacy, I suggest you edit out the “Anonymous UUID,” a long string of letters, numbers, and dashes in the header and body of the report, if it’s present (it may not be.) Please don't post any other kind of diagnostic report, such as a hang report.