Thank you for your answer. As it happens, the bug stopped some time after I reloaded the grub files a few weeks ago. Since then a number of patches have been edited which may have also corrected the problem. I really don't know what happened but now I can enjoy Ubuntu without fearing a crash.
I had no temperature problems. you can close the case. Thank you again -- You received this bug notification because you are a member of Ubuntu-X, which is subscribed to xorg in Ubuntu. https://bugs.launchpad.net/bugs/1737210 Title: sytem restart spontaneously To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xorg/+bug/1737210/+subscriptions _______________________________________________ Mailing list: https://launchpad.net/~ubuntu-x-swat Post to : ubuntu-x-swat@lists.launchpad.net Unsubscribe : https://launchpad.net/~ubuntu-x-swat More help : https://help.launchpad.net/ListHelp