Why is my phone taking ages to start

When I knock on my phone it comes up with optimising app 1 of 1 what takes about 15 mins then starts up to let me put my pin number in then it takes about another 20 mins saying android is starting optimising app 1of 1. I've even done a factory reset on the phone and it is still doing the same and my software is up to date aswel my mobile is the zte blade v7 is anybody else having the same problems