Installation Issues
Some users have reported that Nexus during installation to Android 6.0 Marshmallow, your device has been frozen on the screen for no apparent reason. If you are among those affected, we recommend you wait until your phone's battery is fully discharged and recharge back to 100%. That done, try to update again. Before restarting the installation process, maybe you should try to clear the cache partition team. If you do not know how, here are the instructions:
1) Press the volume buttons (below) and on at a time until the device is restarted and logged in to display Google. Wait until an arrow appears on the screen.
2) Then press the volume button (down) repeatedly until the recovery mode is activated with the arrow symbol. Now just press the power button. You will see Android icon on the screen, with a red triangle and an exclamation point.
3) With the button pressed on, click on the volume up key once and then release the button. It should appear to you a list of options. Use the volume buttons to navigate between them and select Delete or wipe cache partition. Then press the power button again to start the process.
4) messages will appear on the screen. Do not worry. All you have to do now is to wait 10 to 15 minutes for the process to complete. Restart the computer.
If the problem persists, perhaps you can do a factory reset to reset the device. Only access to the section Settings> Personal> Backup and Restore. Enter your PIN or password if necessary and then select Factory data reset> Reset Reset phone or tablet.
Low performance
If you experience problems on your Nexus are underperforming, you can also try to clear the cache following the procedure we have previously detailed. These problems are usually motivated by lack of memory or have a processor with few resources. We also recommend removing those applications that do not use or remove widgets that you have on your home screen and you are not really serving any useful function.
Random reboots
Certain users updated to Android 6.0 Marshmallow Nexus have found that some applications were closed unexpectedly and the team in general was restarted at random. This problem may be due to outdated applications or even small corrupted files that are disrupting the performance. In this case, all I can recommend is that you update regularly your applications and then delete the data and cache memory applications. To do this, you just have to access the section Settings> Applications and select the option to remove data from the cache. If all else fails, maybe you should try a restoration of the factory settings and then try to move from Android 6.0 to Android 5.0 Marshmallow Lollipop.