This is the original Dell AC adapter (or cable) that came with the computer ?

You check in BIOS to see if the AC adapter (or cable) is detected ? If no, please follow steps below:

1. Power off computer

2. Power on computer, quickly start tapping F2 key continuously until you see BIOS menu. Look for the AC adapter type in the BIOS.

How to Troubleshoot AC Adapter Issues on a Dell Laptop | Dell US

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By the way, please list your Dell model number and version of windows.

Example: Dell Inspiron 3543, windows 10

If you don't know, click on the link below and look to the right. You should see it now.

Support | Dell US

hello it is the original dc adapter 45w and i thing it start after  update bios and i have  Dell Inspiron 5558, windows 10

Good to know AC adapter is saying it's type (45w) in the BIOS.

Now, I suspect computer's power management is causing the problem. If you haven't done so yet, try using Power Troubleshooter to fix the problem. Just type Troubleshooter onto the search box, select Additional Troubleshooter, and then Power. Hopefully this will fix the problem.

If above step doesn't fix problem, download / install latest Dell Power Manager lite application from your Dell Product Support page:

Support for Inspiron 5558 | Drivers & Downloads | Dell US

After, right click battery icon at the bottom of the taskbar, select Dell Power Manager Lite app, click on Change Setting, and then change battery settings. Power off computer, wait a few minutes, power on , hopefully computer boot up a lot faster. 

Battery Settings listed below:

Standard - Fully charges the battery at a moderate rate. This setting provides a balanced approach to extending battery life while still providing a reasonably fast charging time. Recommended for users who frequently switch between battery and external power sources.

Express Charge - Quickly charges the battery using Dell fast-charge technology. Recommended for users who need the battery to charge quickly. If the system is powered off, then the battery typically charges to 80 percent within one hour and 100 percent in two hours. Charge time may be longer if the system is powered on.

Primarily AC Use - Extends battery life by lowering the charge threshold, so that the battery never charges to 100 percent capacity. Recommended for users who primarily operate the system while plugged into an external power source.

Adaptive - Automatically optimizes battery settings based on the user's typical patterns. Recommended for users who want to "set it and forget it.

Custom - User selects when the battery starts and stops charging. Recommended for advanced users

If none of the above steps didn't fix problem....

Since the slow start started after BIOS update, I'd suggest considering downgrading or refresh latest BIOS to see if it will make a difference. Please read the article thoroughly in link below. This will help you to decide if downgrading BIOS is best to do.

Downgrading the System BIOS on a Dell System | Dell US