Why does my laptop take so long to boot up?

There can be several reasons, I'm afraid you'll have to do some investigative work.

First, could be viruses and other malware. No security software can catch everything. I personally use BOTH Norton Security Suite and Malwarebytes Premium edition. I would download a couple of free or free demo anti-malware products and use them to scan your system, just in case. There are also some internet based scanners from reliable sources like Trend Micro.

Second is, you could have loaded up your start up file with programs that load on start up that you don't really need to load then. I have found a program called Glary Utilities that can read your start up file and tell you what many of those programs are for, so you can decide if you want to have them loading at start up. There may be free versions of similar programs available, but Glary is not super expensive.

Third is, Windows 10, in many ways, it is the best Windows ever, but the truth is, it is SLOW to boot up and I've found you really need to reboot Windows 10 at least every 2 days for best performance.

Fourth is, you might not have enough RAM. A lot of Laptops, especially the less expensive ones only come with 2 to 4 GB of ram, and EVERYTHING is slower for them!

If you're using Windows 10, right click the taskbar, click Task Manager, then click the Startup tab.

It will list your startup programs and say how much they affect your startup speed. Research those and remove the ones that aren't needed. Just be careful not to remove critical stuff.

I would also look into defragmenting the hard drive, and check the SMART data for your hard drive to see if it's going bad.

are you using onedrive?

my i7 machine was lagging beause it was linked to one drive. one drive stores all your information your computer. when you start up your machine and when it shuts down. i had my computer save my info on my machine instead of one drive and my machine ran much faster. one drive tries to sync with your computer when it starts up and when it shuts down.