I not only had lag after unlock, but also many times while using the phone. I was extremely pissed and was ready to take it back, then I found a posting about lag with the recommend procedure below. After turning off the transitions, no lag. Runs smooth as silk.
So, try this:
Settings/Developer Options/Drawing - Set all of the below to Off. (Some have said .5. You can try that if you want)
- Windows animation scale
- Transition animation scale
- Animator duration scale
It solved my lag issues.
(If you don't have developer options do this)
Settings/About phone/Software info - Then tap on Build number repeatedly until Developer Options is unlocked.