If your Mac is behaving in an odd way, there may be an issue with some piece of the hardware -- such as the RAM.

You can perform a hardware check in order to chase down a diagnosis.

• Shutdown your machine
• Boot your machine
• While it is booting, hold down the d key

At this point, the machine should have booted into a special hardware check mode. Select your preferred language, the hardware check will be performed, and any issues will be reported.

h/t Dillon Hafer