public OnPlayerTakeDamage(playerid, issuerid, Float: amount, weaponid)
{

    HeadSacertos[playerid]++;
    if(HeadSacertos[playerid] == 4 && HeadStick[playerid] > GetTickCount())
        return Kill(playerid), SetPlayerHealth(playerid, 0);
        
    HeadStick[playerid] = GetTickCount() + 3000;
    return 1;
}

OnPlayerSpawn ..

HeadSacertos[playerid] = 0;