If you are having issues watching on a built-in Smart TV (Samsumg/LG/etc) here are a few things to try:
Common fixes
Check for app updates
In the TV's app store check that the app is the latest version and if any updates are available
Clear Cache
TVs running out of space/memory will cause buffering/freezing
LG TV: https://www.lg.com/ca_en/support/product-support/troubleshoot/help-library/cs-CT52001643-20153751792833/ Samsung: https://www.samsung.com/au/support/tv-audio-video/clear-app-cache-and-data-on-your-samsung-tv/ Google TV: https://support.google.com/chromecast/answer/11276506?hl=en
For specific instructions, Google your TV brand/model + clear cache
Article with more info: https://www.zdnet.com/home-and-office/home-entertainment/how-to-clear-the-cache-on-your-tv-and-keep-it-running-like-new/
Turn TV off at power point for 30 seconds
This can help by restarting the apps and clearing any memory issues
Connect to modem with cable intead of Wifi
An Ethernet connection will be faster and much more reliable than Wifi
Run a speedtest on your TV
You may get good internet/wifi speeds on your phone or laptop but your TV could be far worse See if your device has a speedtest app or open/install a web browser from your TVs app menu and visit https://speedtest.net Most TV show episodes should play fine with speeds above 15mbit, some movies are higher quality requiring 30+mbit.
Still buffering? See Speed — what a speed test doesn't tell you for why a fast speed test doesn't always mean fast streaming, and Buffering & Speed for what to try next.
Upgrade to a streaming device
See Streaming Devices for details.