My cellphone auto power on | Nokia auto power on

Insert batteray, cellphone automatically power on :
1. Check / clean the cellphones for water damage, oftentimes auto power on caused water damage
2. Check switch on/off (power button), using ohm meter, change if switch short/broken
3. If the problem not solved, check power IC
example : Ic CCONT , Ic UEM ( universal Energy Management)
4. If the problem not solved, probably main circuit short.