I am using mobile to reply. Can't get into messages due to some reason. Yes, service tag is right. Please send me an email if want to talk personally.

Please list exact Dell model number and version of windows. 

Example: Dell Inspiron 3543, windows 10

If you don't know, enter the service tag number onto the link below. You'll see exact Dell model number in your Dell Product Support page.

Support | Dell US

How to find a Dell Service Tag (Official Dell Tech Support) - YouTube

In meantime, run Dell Diagnostic to check the hard drive and other hardware within the computer. 

You could do this by following steps below:

1. Power off computer

2. Power on computer, quickly start tapping F12 key continuously until you see Preparing One Time Boot Menu in top right corner of screen. In Dell Preboot menu, select Diagnostic. Report back any error code.

Dell Diagnostic Tools to Diagnose and Fix Hardware Problems on Your Dell Computer, Tablet, or Server...

Dell Inspiron 3567, Windows 10. There are 3 Amber lights and 5 white lights coming continuously. I went through previous post and there seems be no ultimate solution for this code. 

It started many times by trying all this, doing this daily is so frustrating, I have now updated the bios firmware and this is not starting. What is the complete solution ? I need to try this hours and then it switches on. This is frustrating. We expect better things from Dell. I see many facing similar issues.

Three Amber lights and five white lights means Power Rail Failure. Dell Inspiron 3567 supports Real-Time Clock (RTC) reset function. 

The RTC reset function will reset the BIOS to factory default settings and reset the computer date and time. 

Please follow steps for the RTC reset in the link below, hopefully this will get computer up and running again. .

How to Reset Real Time Clock (RTC) to Recover Your Dell Laptop | Dell US

I called a repairing guy. He told the motherboard needs to be repaired or installed as the system is starting and switching off both together. What I can do now?

I didn't use the laptop for one year much and then when I started using it the keyboard buttons pressed automatically. When I used the laptop for 1 year 3-4 months using external keyboard and this issue now. I relied a lot on dell as being from the tech field I had heard a lot of good things about dell. I will never buy a Dell product after such an experience. The motherboard getting problem after 1 and a half year usage destroys me mentally. Covid time I already faced lot of trouble due to the keys auto pressing.

If you aren't comfortable opening computer base cover or all your troubleshooting failed then it's time to get a quote from the repair man that you contacted or contact Dell Technical Support in link below:

Contact Information | Dell US

Or 

Arrange an 'Out of Warranty' repair on your Dell System in link below:

How to arrange an 'Out of Warranty' repair on your Dell System | Dell US

Thanks for all the updates and feedbacks. Good luck in your search for repairs.  

The system starting on and switching off continuously is one of symptoms of a faulty motherboard, and you include three Amber lights and five white lights for Power Rail Failure, tell me it's a possibility that your computer is experiencing an issue with the motherboard.

Now, if you are comfortable opening the computer base cover and removing components inside the computer, I suggest reseating coin cell battery to see if it will make a difference. Removing coin-cell battery will resets the BIOS setup program’s settings to default.

Note: Leave the coin cell battery out for a few hours before replacing it back into the base.

Please view the removing / replacing coin cell battery in Service Manual in link below:

Support for Inspiron 15 3567 | Documentation | Dell US

Also check out the information in link below, hopefully it will be a help to you:

How to Perform a BIOS or CMOS Reset and Clear the NVRAM on Dell Systems | Dell US

EDIT / Service Manual / Coin Cell Battery

If it is a motherboard issue, then how removing the cell will help? I had called the mechanic but he didn't remove the cell and check it. He said must be the motherboard. Didn't expect dell laptop motherboard to cause so much trouble in a year. The start year and so I didn't use it much. I had purchased it in August 2018 and didn't use much a year or so. Used it more during covid times.