TV sounds weird after about 2hrs of being on

Hello,

im wondering what’s going on with my Toshiba tv. It works great, picture quality, sound, everything seems normal EXCEPT after a few hours of watching tv, everything starts sounding robotic .. any show I’m watching sounds weird and all I have to do is turn the tv off and back on & it goes back to normal. Does anyone know how this could be fixed or what may be causing this issue?.