It is a diagonal trace because the source of your noise is drifting in frequency. We see that the noise floor to the right of your receive frequency is lower than the noise floor to the left.
If you set your receive mode to CW, SSB, and AM, respectively, do you hear anything? Sometimes the changing energy level that raises and lowers the noise floor does not create noise that the receiver hears. From the looks of the irregular trace it might sound like a buzz saw.
Your overall noise floor on 20 meters seems to be very high. I am accustomed to seeing -110 when near a city and even lower in a very quiet location. Your noise floor appears to vary in the mid -90's.
This is an opportunity to use your 6300 as a test instrument. If you widen the receiver as wide as it will go you will probably see a recurring pattern of rising and falling energy. Document the periodicity of the peaks. Many of use on the Community had a lot of cumulative experience in tracking down noise. KY6LA did an excellent job of documenting avoidance techniques. If you document the entire spectrum that your 6300 covers that will give us a chance to identify the likely culprits. It is a lot easier to search for a noise source if the emitter is narrowed down to one or a few likely sources.
Let us know what you see and hear and we'll try to assist further.