Hi Dhana,
Thank you for posting your question in the Microsoft Community Forums.
Based on the information, you are unable to get sound when you switch on the laptop and sound will come back after a restart. Also when the laptop is not used for 15-20min it goes to Sleep mode.
It would be helpful if you could reply to the questions to assist you better.
- Have you made any recent software or hardware changes on the system?
- Do you have any external speakers connected?
- What is the exact model number of the HP laptop?
Let’s try the following steps and check if it helps.
Method 1:
Check to see if the computer speakers are set to be default.
a. Open the classic Control Panel by typing "Control Panel" at the home screen and clicking the "Control Panel" icon.
b. In the Control Panel navigate to "Hardware and Sound" and then click "Sound".
c. On the Playback tab, select the speakers and then click the "Set Default" button.
d. Click or touch "Apply".
Method 2:
You may try running the Audio troubleshooter and check if it helps.
Method 3:
If the issue persists, you may try to uninstall and reinstall the sound drivers and check if it helps.
Step 1:
Uninstall the graphic card drivers.
a. Right click on the bottom left corner on the desktop (on Start Screen) and select Device manager.
b. Expand Sound video and game controller and right-click on sound driver and select ‘uninstall’.
c. Restart the computer.
Step 2:
You may also try to install the latest version of sound card drivers for Windows 8 from HP support website and check if it helps.
If Windows 8 drivers are not available, you may try installing Windows 7 drivers in compatibility mode and check if it helps:
Follow these steps to install the drivers in compatibility mode and check if that helps.
a. Download the driver from the manufacturer’s website.
b. Right-click on the driver setup file and click on ‘properties’.
c. Click on the ‘compatibility’ tab and check the box ‘Run this program in compatibility mode for’ and select Windows 7 operating system from the drop down menu.
d. Click on ‘Apply’ and click ‘OK’ and run the file to install it.
Regarding the sleep mode issue, you may try changing the Power option settings and check if it helps.
Method 1:
You may try to install the latest version of Chipset and graphic card drivers for Windows 8 from HP support website and check if it helps.
Method 2:
You may also try the following steps and check if it helps.
a. Open Power Options by swiping in from the right edge of the screen, tapping Search (or if you're using a mouse, pointing to the upper-right corner of the screen, moving the mouse pointer down, and then clicking Search), entering Control Panel in the search box, tapping or clicking Apps, and then tapping or clicking Control Panel.
b. In Control Panel, enter Power in the search box, and then press Enter.
c. Change when the computer sleeps and select "Never" for sleep option.
Check if it helps
For further information, refer to the article:
Power plans: Frequently asked questions
http://windows.microsoft.com/en-in/windows-8/power-plans-faq
Hope the information helps.
Let us know if you need further assistance with Windows related issues. We will be happy to help.