Every now and then, I turn on my phone and my lock screen freezes. Why

Every now and then, I turn on my BLU Life one x2 and my lock screen freezes, forcing me to turn off my phone and wait a few seconds until I can turn it on again. And even then sometimes it doesn't work. How can I fix this?

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crwdns2934109:0crwdne2934109:0

crwdns2889612:0crwdne2889612:0 0
crwdns2934285:0crwdne2934285:0