MY PC restarts when sleep mode entered

I have a rather serious sleep/ restarts issue with my HP Ellitebook 8440p processor intel core i5. The issue does not seem to depend on the OS, windows and now with ubuntu 16.04. After entering the sleep mode, my laptop restarts about two seconds after sleeping. I've tried many things to solve it, but none of them did the job. At the first time there were no such problem. I have the 64 bit version of 16.04 installed. The behavior is independent from a power cable/usb device/ethernet cable being plugged in. I know there have been several treats concerning sleep/ restarts issues, but none of them provides an answer to my specific case. If you have an answer or even a clue on how to solve this issue, it will be highly appreciated! Thanks in advance!

Solution 1:

I have the same problem with my Lenovo Laptop that runs on Ubuntu OS.

When I close my laptop lid or press sleep it goes to suspend mode completely and it is normal, But when I open lid and press any key Ubuntu reboots.

I search lots of stuff for this solution and I got a solution that work fine for me, Let me tell you what I was done...

1. First you have to edit /etc/default/grub file

sudo gedit /etc/default/grub

2. Look for the line

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"

3. Replace above line with

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_sleep=nonvs"

4. Just Save file and close it.
5. Now you want to update configuration of boot loader

sudo update-grub

6. After that reboot your system.

I hope this will help you to solve your problem.

Solution 2:

Finally i solved it. I upgraded the BIOS and reset CMOS setting by removing CMOS battery and waited for 30 minutes then i put the battery back again. The problem solved!