Unable to unlock/turn on Nexus 4

I am running Android 5.0.1 on my Nexus 4. This has started happening recently. Whenever my phone is locked, and I try to unlock, nothing happens on pressing the power button. Initially I thought my battery was getting drained to zero and phone was shutting down, but that's not the case. I need to long press power button and restart my phone forcefully. Some observations are:

• This issue was not there when I was on 5.0.0.


• Also I am finding that this is happening when I play a game and then close the game and leave the phone. Most recently, I have been playing Swish and Drift Zone.


• However, even after uninstalling the issue persists.

Any suggestions/references are welcome. TIA.