After 2 - 4 hours my laptops starts showing me black screen when when I click somewhere. This has happened many times and it happens only when my laptop is awake for a long time and a lots of tabs are open. (Firefox and multiple terminals in diverse workspaces) I do suspend it for 5 or 10 minutes by closing its lid. This problem happens more when more than one terminals are open.
Also i had not changed any graphics card.
Acer Aspire 5742
Intel Core i3-370M
4 GB ram
Intel HD graphics
Triple boot (Ubuntu Mate 16.04, CentOS 7, Windows 7)
i am new to this site,so please forgive if i made any mistakes.