Default [Q] LG optimus G 970 Screen blank on wakeup


I have a mobile phone LG e970 which is having a issue in display of phone. The mobile brightness is very low when the phone wake-up after sleep mode however if I restarted my phone the its works fine. I also tried this after set the mobile brightness 100% but this issue is not resolved. Can anyone help me to debug this issue? I am not sure is it an hardware issue or software issue.