Nexus 5 gets lock automatically

[AC Question]

I purchased nexus 5 two weeks ago. I set up the pattern lock. now i am facing a problem that the phone gets automatically locked with some code and to remove it i have to factory reset the data for that. several times i have reset my data. please let me know what should i do.

 

[B. Diddy]

So does it suddenly show a lockscreen that requires a PIN or password, even though you set a pattern lock? Or do you get some other popup message asking you for a code that you don't know? Did you get the phone new or used? If new, I would take it back to the store and ask them if they can do anything. If used, talk to the seller and see if the phone was modified somehow.