Your Mac, is running at OSX High Sierra, Yosemite, Mavericks and facing problem on not saving data for volume control level, Screen resolution, Disk selection and useful information those should be stored in memory when your Mac(MacBook Pro, MacBook Retina, iMac, iMac Pro) not on plugged with power or Shutdown. Apple store all the setting and data those set by device owner and not should be changed when it will come to work. Here I explained about NVRAM (non-volatile random-access memory), in which case you should reset and how to do.
Note: Data Storage way in NVRAM, setting, and options might be different depending on which Mac model you have. But you can reset NVRAM on Mac OS X running on Yosemite, Mavericks only below given steps.
In which case you need to Reset NVRAM memory and whole setting
Speaker volume not saved
Disk selection should be changed on each startup
Kernel Panic information not be saved
Step to reset NVRAM on Mac OS X: MacBook Pro, MacBook Retina, iMac and other
In this process, you need to use shortcuts for NVRAM setting reset.
Step 1: Put your Mac Shutdown,
Step 2: Press and hold keys from keyboard: Command + Option + P + R.
Step 3: start your Mac.
Step 4: Before to hear the startup sound on your Mac device, Press and hold Command + Option + P + R.
Step 5: Wait for restart your device automatically, continuously hold keys and release all the keys after listen startup sound on second-time release all the keys.
In the whole process, your Mac restarts two times.
Now you erased all the data stores in NVRAM memory as a Speaker Volume, Screen Resolution, Startup disk selection, and Time Zone information.
Note: Reset NVRAM might resolve Wifi connectivity issue after update your OS X.
For Safari: Cookies Settings, Reset safari on Mac and PC [Steps].
Now you need to reconfigure all the setting erased by this process likes speaker volume, screen resolution, Start-up disk, and your Time Zone selection.
If you are not a success on Reset NVRAM on Mac OS X devices iMac, iMac Pro, Mac Mini, MacBook Pro, Air and other, then you feel free to contact on-line apple support.