Default [Q]Galaxy S2 i9105P Soft keys

Hello , I have an Samsung Galaxy S2 i9105P with 4.2.2 stock .
The problem is when I unlock the phone , when I touch first the soft keys he respond after 20-30 seconds , it's a sort of delay or i don't know but after that he works really nice .
EDIT: i forgot , sometimes i have the same problem with power button .
What can I do?