1. Firstly, restarting computer wont affect your internet performance, you might have to restart your modem instead
2. Make sure there are no programs are running in the background that using your internet connection, some programs are needed to be updated automatically with/without your permission
3. Run antivirus and scan your computer, viruses can reduce your internet performance stability
4. You might try another DNS, google DNS for example
8.8.8.8
and 8.8.4.4 ( For alternative one ), pic is attached.

Good luck