Without any other details a good 1st step would be to determine if it is the connection to your router vs your router's internet connection to your ISP.
To check the router, make sure your connection to the router is stable and when you log into the router check the uptime and connection stats. If you are loosing wifi or hard-wired ethernet connections the net connection status will have some info, and best confirm between multiple PCs to determine the router as the suspect.
If all is well on your end, it's probably the latter so call your ISP and have them check the line, they should also tell you to reset your modem and/or router when on the phone with them as they check. This will either confirm there are no problems with the connection to your house / modem / router or they will send someone to fix.