Windows 10 in itself has a few issues at start up. It'll typically install updates and do system maintenance when you first boot up. They can take some time to complete and can impact the performance of the device sometimes.
If your iPad works fine, and your speeds are fine when you run SpeedTest, then I would look to your computer and operating system as the culprit as @Nighthawk suggests. It is exceeding unlikely that the 'Internet' would slow, just because you have restarted your computer. If you have live tiles, they, too, are downloading new information at start.
I'd recommend a better browser as the old MSN one should not even exist with Windows 10, unless you mean Microsoft Edge. Try Firefox or Chrome and see if there is a difference.
Hi bandl, I had a different issue on my laptop since getting the Windows 10 update, mostly when I was powering off my computer. I had to turn off fast startup but in your case, it may help. Have a look here http://www.tenforums.com/tutorials/4189-fast-startup-turn-off-windows-10-a.html and let us know if it's helping. Nighthawk's suggestion is also good, I personally use Chrome in my PC.