Hello and welcome to JustAnswer!
Any time the light comes on there will be fault codes stored in the module that controls the pressure monitoring. If all tire pressures are set at 36 PSI when the light is on then it's pretty likely that you have a problem with one of the sensors, and it will have set a fault code (a fault code setting is the sole reason the light illuminates).
You may have a sensor that is bad, or one that has a low battery. The batteries in the sensors do have a finite life, and yours is coming to the age where the batteries will be low enough to set this message off. The batteries are part of the sensor, and a sensor with a low battery would need to be replaced.
It's going to be a matter of connecting a scan tool to the vehicle and retrieving the stored fault codes related to the tire pressure system. As long as the battery isn't disconnected between the time the light comes on and the time you get to the dealer, the codes will still be stored.
If it's a low battery it's hard to say why it would come and go like that. A low battery should keep the message there until the sensor is replaced.
If a sensor just wasn't producing a signal intermittently, then that would explain why the message could come and go. There are also trigger modules in the system, which read the signal from the sensors in the wheels. Any of these could cause the problem also.