Screen problem - cannot hard reset

[utherpendragon8765]

After using my M8 normally earlier today, and with no previous problems in my year or so of owning it, I pick it up this evening and find the whole screen is an all-over purplish-white - like "white noise" on a tv screen except that the pixels aren't moving. If the screen is off, it's black, if it's on, it's this "white noise".

Tried soft reset (power+volume up) - the M8 doesn't actually power down properly, the screen is unchanged but the welcome sound is audible.

Tried to hard reset (volume down, +power) - the screen doesn't change from the "white noise" so impossible to hard reset.

Help! :-[

 

[utherpendragon8765]

After a couple of hours of this, and me doing nothing other than the things listed above, this has suddenly corrected itself and the phone is back to full functionality.

Any thoughts as to why this happened and whether I have a component failing/about to fail? Should I be thinking towards repair or replacement?

 

[Mooncatt]

Sounds like a component failing, but no clue which it could be. Repair could be costly, though.