My car is starts on its own........ (searched)

ok so my alt went bad so i got a used but still working one from a friend i get it and on the way home my batt light came on

i switched the alt and now when i try and put the groung on the batt it sparks and the car starts to crank on its own and i change the starter also put the ground on the batt it starts cranking

i went thew
3 alts
2 starters
4 batts

PLS HELP i dont want to get rid of it :bawl:

its a 90 gs 4 door full wire tuck fuse box under the dash batt in the trunk 400 watt amp for my components 7ch equalizer fog lights wired to rear defrost swich the motor has 5 4gauge grounds if that helps