I was driving down the highway, suddenly LCA block pops up on the cluster. Please see attached. But once I restart the car it's gone and dealer don't know what the issue is

 

Looks to be the Lane Change Assist sensors. Either something disrupted their signal or perhaps the sensors just malfunctioned for a moment.

 

Clean the sensor and you are good to go again.

 

Did you find a fix for this issue? I have a 2012 Porsche Panamera and I’m receiving the same error.

 

Suggest Googling "Porsche Lane Change Assist Sensor." Porsche uses the same technology/parts among several models. Seems that intermittent blocking/failure is not uncommon.
Usual dealer remedy is to replace all sensors, which not only is expensive but also is not a guaranteed fix. Sometimes the problem persists after sensor replacement.
All too often these electrical problems are due to insufficient/bad electrical grounds. Body ground connections do degrade with age and corrosion. Chasing down ground connections can be frustrating as they may be hard to see or find, so I have just made a new ground wire connection in some instances.
Another potential cause is low voltage to the sensor. Car batteries do degrade over time. I replace them every four years, no matter what. These modern sensors are very sensitive to less than optimum voltage; and while your battery has enough energy to start your car it may be lacking a bit in running voltage.