Diagnosis
This is an HDMI handshake or bandwidth issue. The TV and soundbar are briefly losing sync on the audio signal.
How to Fix It
First, replace the HDMI cable. Use a certified High-Speed HDMI cable. Ensure it is firmly seated in the TV's ARC port and the soundbar's HDMI OUT (TV ARC) port. On the soundbar, go to Settings > HDMI and set 'Audio Format' to 'Bitstream' instead of 'PCM'.
If That Didn't Work
On your Samsung TV, go to Sound Settings > Expert Settings. Turn off any 'HDMI Audio Format' or 'Digital Output Format' auto settings. Manually set it to 'Dolby Digital'. Also, disable any TV sound processing like 'Adaptive Sound'.
Heads Up
Some Samsung TV firmware is known to have ARC bugs. Check for TV software updates. If the problem started after a TV update, you may need to wait for a patch or use an optical audio connection instead.