XPERIA X8 will Automatic ON when Charge, Why?

[royslowly]

According to my experience, the phone will always start (upto the charging battery animation) while charging in OFF mode

this is the correct way and status i also observed before when i charge my phone (SE X8), but not on my phone now... it will really start and fully boot to the homescreen even if i will shut it down... it will turn on again and boot ... why ?