While I'd check the warranty and if inside warranty make the call so you get a ticket number to keep in case it fails altogether, I want to ask what the Internet has to do with the TV. Netflix and such could delay in the feed and cause strange issues.
Since there is no sound bar in play that's not it. The only test to do is to try another set in place of this TV. If that works in the same place and connections, it's something wrong with this TV.
The only user serviceable items follow.
1. Make sure the TV firmware is current. I defer to samsung support on how to check and install.
2. Try a factory reset. This will be in the product manual. If you tossed it or didn't get one, that manual is up on Samsung.com
I'm experiencing issues with the sound on my Samsung Smart TV, Model Code UN48J5200. When I turn on the television, the sound works fine for about a minute, then goes out for a few minutes, after the sound resumes it is fine for the rest of the time that I have the television on. This happens every time I turn on the television. I've replaced the cable box and HDMI cable, disconnected my Sonos soundbar, and checked my internet connection. The problem persists. Anyone else experienced this issue or have any thoughts on what may be going on?