volume adjustment error on nexus 5 running 4.4.4

[AC Question]

something is not right with my nexus 5. for the last 2 days the volume adjusment bar pop up by itself every now and then and stay on the screen for random timing, sometimes its there for a full 2 minute or so and naturally i cant touch anything underneath it. and if i try to adjust the volume it will turn back up to full volume. even when it doesnt come up automatically i still cant adjust volume, everytime i turn the volume down it will go back up to full volume straight away.
and sometimes the power button is not working as well. the option for turning off phone or plane mood doesnt come up after i press the power button, and if i keep pressing it the phone goes into restart straight away.

so far the most annoying is the volume adjustment that keep popping up when i am using the phone.

can anyone advice me what to do to fix this probem. i try switching off my phone when i sleep to let it "rest" and take it out of its casing (incase the problem is something physical with the casing) and it didnt help at all

thanks all

 

[RumoredNow]

You could reflash the system without loosing user data. If you are comfortable flashing via fastboot...

Or you could get a warranty replacement. Hard to say if it is hardware yet or a bad update to 4.4.4...