My screen stops working unnecessarily, the screen and touch work

So I was using my Nexus 5 and suddenly white lines started appearing and the screen went black and wont turn on again although the phone was on.I switched it off and entered into the bootloader and wiped my cache(It is the problem most of the times). The phone successfully restarts, Touch Works, screen works, sound works, everything works, after an hour of use white lines appear again the screen goes black, I turn my phone off , but now I am not able to get to the bootloader. Please note: I cant get a replacement or cant even open it as i am not allowed to do so (my mom doesn't). As everything works fine I don't think I actuall yneed a replacement