Mac Mini 2018 goes to black frequently.!?

Hi im using mac mini 2018 model. My problem was external monitor goes black 2-3 second frequently in the middle of using it. I'm using mojave 10.14.6 version and dual monitor setup one was benq 27inch monitor was using hdmi cable to hdmi port in mac mini another one was vu 43ich 4k tv to connect thunderbolt apple usb- c av multiple port adaptor to hdmi cable (cablecreation ultra high speed hdmi cable).

Please help me. Thank you