Loud popingggggggggggggg when i turn the amp on and off....rawwww

All amplifiers are designed so that when you first turn it on the sound increases gradually so the voltage spike caused by turning it on doesn't get amplified. The problem is in the amp itself, and only good electronic technician can fix this problem. You can't fix that yourself, but I will give you an idea of how a car amp works.
A car amp actually operates in roughly 70 volts DC. It takes the 12 volts, and steps it up to two voltages of -35V and +35V. It accomplish this by a circuit called SMPS or switch mode power supply. There is the preamp circuits then the power amp circuit. Music is fed to the pre amp, through series of filter circuits which filter out the high frequency for example so you end up with only the bass.which can be adjusted to your preference. The actual amplification goes through many stages to provide a clean distorted free sound. The final stage is the big transistors that actually drive the speakers. Usually there is a slight delay for the power amp circuit to come on that way it wont amplify the sudden surge of current when it is turned on. Some house amps uses relay in series with the speaker that has a timing circuit, and you hear it click a few seconds after you turn on the power. Relays are not used in higher powered amps. One way to fix this problem is using relays that has a timing circuit that comes on after a few second after the amp is turned on. You can put it in series with the positive side of the speaker, but only if its not a very powerfull amp. Maybe up to 600 watts. Higher powered amp may burn the relay contacts prematurely. You can learn to build simple timing circuits to drive relays. They only use a few parts, and maybe use a breadboard to test them. Don't try to mess with the inside circuitry on your amp, because they are very sensitive, specially the SMPS circuit. I hope this is helpfull.