That suggests an unstable connection between your router and the telly. Disconnect the power from your router, wait a minute or two and then reconnect the power. (You'll then have to wait a short while until the router fully resets itself). That can often fix such problems.
Also though think about where your telly is in relation to your router. If you can get them closer together, do so.
If your router is of the type that has aerials projecting from it, make sure that they're in the correct positions (as shown in the manual for your router).