There are a couple of things you can try. First, unplug your router for 60 seconds, then plug
it back in and let it boot up.
I'm thinking you're likely using Windows 10 so right-click the start menu button and
select Device Manager
expand the entry for Network Adapters,
right-click on the wi-fi adapter and Uninstall
close Device Manager
Right-click the start button again
and select Command Prompt(Admin)
At the blinking prompt in the black window type the following commands, pressing Enter after each:
netsh winsock reset
netsh int ipv4 reset
netsh int ipv6 reset
Restart the machine. Windows will re-install the wireless adapter
and reset the networking protocols.
Connect to your just-re-booted router and see if you have a stable connection.