Check out msconfig -> startup to see how much stuff is being loaded at the startup. Also check the number of running processes in the Task Manager after a reboot. Check the settings in your anti-virus software. Look in the device manager for unidentified devices and otherwise check that you have the latest drivers
for your hardware.
Basically, very often the laptop manufacturers will install lots of bloatware in their products and all that stuff wants to run all the time. My new Sony laptop was running 90 processes in its maiden form! Naturally, it takes time to load all that stuff.
In addition, depending on the scheduled tasks and anti-virus settings the computer may be running some scans at start-up. My anti-virus is set to run a quick scan at start-up, but if at some point I want to do a deep scan and then forget to change settings, it will try to do the deep scan at the boot time, which will tremendously slow things down.
And of course there might be a driver
problem. Are you running the pre-installed OS, or did you do a (hopefully) clean re-install? Sometimes - as was the case with my new Sony Vaio - Windows will not automatically find the right drivers. Results may range from low screen resolution to unidentified hardware to slower boot times (since Windows will try to do something about that hardware at boot time as well).
Any of the above may be your problem. There might be something else as well. A lot of people will advise you to run a thorough virus scan and also a scan with Malwarebytes or a similar anti-spyware product. I have personally never experienced any such problem (all scans are always negative), but this does not mean such problems do not exist.
Hope that helps.