More serious problems
What does a flashing question mark on startup mean?
Your Mac can’t find a drive to boot macOS X from. The first thing to do is wait, because occasionally a minor problem causes this to happen as a one-off. If the Mac eventually starts up, go to System Preferences > Startup Disk and select your startup drive. If not, try Recovery (see “How do I use Recovery to get my Mac working again?”, below right).
Could resetting the NVRAM or SMC help to solve my problem?
Non-volatile RAM (along with PRAM,
