I've had my 2018 CX-5 for four years and just noticed the horizontal white lines on the driver info display. Is this normal? Does anyone else have this problem?

 

have to had your car on recall. their is a recall for these vehicles . for the computer reprogramed. Or upgraded

 

My 2021 has these lines and they vary depending on how the vehicle avoidance sensitivity on the cruise control is set. I don't know if this applies to a 2018.

 

They are Lane Assist lines.Vehicle lane line display

When the LAS & LDWS becomes operational while on standby, the vehicle lane lines are displayed in the multi-information display and the active driving display. In the vehicle lane lines display indicating the operation status, the color of the vehicle lane lines being detected changes to white.

(Stand-by status)
(Operational status)
Auto cancel

In the following cases, the LAS & LDWS is automatically canceled, the LAS & LDWS warning indication (amber) turns on, and an alert is displayed. When the LAS & LDWS become operational, the system turns back on automatically.

• The temperature inside the camera is high or low.
  
• The windshield around the camera is foggy.
  
• The windshield around the camera is blocked by an obstruction, causing poor forward visibility.
  

Auto cancel of warning/steering assist

When the following operations are performed, the LAS & LDWS operation is canceled automatically. The LAS & LDWS resumes automatically after the operation.

• The steering wheel is operated abruptly.
  
• The brake pedal is operated.
  
• The accelerator pedal is operated.
  
  (To cancel the automatic sensitivity cancel function, deselect “Cancel sensitivity” in the personalization features setting.)
  
• The turn signal lever is operated.
  
• The vehicle crosses a lane line.
  

 

HORIZONTAL Lines

 

Sorry, copy/pasted the wrong page.
2018 Mazda CX-5 Owner's Manual | Mazda USA
The HORIZONTAL lines show on my 2020 for the DRSS front radar system when the "radar" sees something.
That said you could have an issue though I have seen nothing on this in any TSB or recalls.