Pioneer GM-6500F Protection mode light on and off

every morning my amp is working and after a few drives lets say 2-3 shutting the car and turning it back on the amp kicks into protection mode. its the second day since installed. i have checked it before on a pc psu and a random aftermarket headunit i had and computer speakers and it worked, i decided to put it on my car and route full car amp kit and it worked. my brother just took it off his car.. its cooling down and even a few hours still cant get it on. i have tried removing all speakers and checked still nothing. also all rcas out still the same. its like the wires are brand new the speakers ohms match with it and rms is good for that amp i dont get why its happening..
well its kicking into protect when i am on acces and starting car dosnt make a diffrence.
and it does not say which type of protect mode i just read online that if the power light is flashing its protection mode and if its solid its working ok.
this is the same as my amp and same wires are connected but hes problem is basic rather than mine
video example
Hi, here is some basic testing you can do:
Connect it to a car battery and a charger (may be your PC PSU instead of a charger). Connect some cheap speakers, just to have a load at the output.
You may short the input RCA or connect some head unit, that doesn't matter.
Switch it on.
Take a voltmeter (only in V position!) and check the voltage at all speakers cold and maybe after 4 hours. Write down!
Report these numbers. Something up to .2 V (or 200mv) is always OK. The value may change over time due to warming up, but should stay about that low.
The amp will have a threshold which makes it cut out. This is one safety measure.
There will be a temperature limiter, too, maybe also a control circuit for internal voltages.
Don't expect anything fancy inside an average car amp.

If outside the car the amp behaves just normal, there is the possibility of a fault in the device connected to the amp. If you use an active x-over, try the amp without it. If you only use a head unit, change it. The device feeding the amps RCA may have a DC output or oscillate, both is not audible and may trigger the protection after a while. You may also just connect some smart phone or MP3 player to the RCA instead of the current source and leave the stuff in the car while driving. Check output voltage as long as it works! When protection is enabeled there will be zero volt anyway.
Maybe do the in car test first, then the one on the bench.

These amps have very low production cost and are operated in a vibrating car, they may have a loose screw pressing a transistor to the heat sink, dried out thermal conductive paste, something bend or just a loose solder joint. All of these faults can lead to a temporary shut down. I once had an amp that quit after a while, but only when put on a car carpet. They forgot to put some isolation under the PCB which shorted a solder point to the metal housing when pressed on. China is incredible creative making cheap mistakes.

You probably are no electronics guy, as you would not ask if so. If these tests do not show a conclusive result, give it to someone who repairs such amps for a hobby. You didn't mention the make and model of the amp, so I suggests it is something cheap.
Before spending money on such a unit, check eBay and the like for the used price. It is impossible for someone paying taxes to fix even a simple fault on this thing for less than 100$. Something simple would be an easily detectable solder joint for example. As soon as you have to order parts, the cost hit's the roof.
So maybe better get another amp and sell this one as defective on some platform, for a few $.
Sounds like early class D car amps that would go into protect after running and cooling down after turning off the car.

Next startup amplifier stay in protect mode.
You would heat the amp with hair dryer and protect turn off.

In video he said start up slow when new
over time got worse.

sounds like amp is junk.
another junk class D to add to the list.
or power supply is not well designed
and easily false triggered