Display of user icons on log-in screen

Boot into Safe Mode by booting with the Shift key held down and check there to see if the problem persists.  Reboot normally and test again.

NOTE: Safe Mode boot can take up to 10 minutes as it's doing the following; 

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files

First, there is no reason to ever install or run any 3rd party "cleaning", "optimizing", "speed-up", anti-virus, VPN or security apps on your Mac.  This user tip describes what you need to know and do in order to protect your Mac: Effective defenses against malware and other threats - Apple Community. Additionally unless you're using a true VPN tunnel, such as between you and your employer's or bank's servers, they are useless. Public VPN's are anything but private.    So if you don't need the Cisco software due to employer's requirements I'd uninstall it also.

That being said you've installed what most of the experienced users in these forums consider akin to malware, CleanMyMac. Uninstall it according to the developer's instructions.

Also uninstall Flash and PepperFlash. Flash support was dropped by Adobe at the end of last year and can pose a security threat. It's a dead app and should be avoided.

You have quite a few apps opening at boot in the System/Users & Groups/Login Items preference pane. That is causing a strain on the memory. Only the absolutely "must have" apps should be launched at boot. The others, like Speedtest, can be launched manually when needed and closed when done.

You can check to see if you've removed all of the supporting files of the apps you want to delete by downloading and running Find Any File to search for any files with the application's name  and the developer's name in the file name.  For CleanMyMac software you'd do the following search(es): 

1 - Name contains cleanmymac

2 - Name contains macpaw

Any files that are found can be dragged from the search results window to the Desktop or Trash bin in the Dock for deletion.

FAF can search areas that Spotlight can't like invisible folders, system folders and packages.  

If the drive is an SSD driver there are no moving parts so putting it to sleep is not really advantageous.

Download and run Etrecheck. Etrecheck is a diagnostic tool that was developed by one of the most respected users here in the ASC and recommended by Apple Support  to provide a snapshot of the system and help identify the more obvious culprits that can adversely affect a Mac's performance.

Copy the report

and use the Additional Text button to include the report in your reply.

IMPORTANT:

Before running Etrecheck assign Full Disk Access to Etrecheck in the Etrecheck's Privacy preference pane so that it can get additional information from the Console and log files for the report:

Also click and read the About info to further permit full disk access.

Then we can examine the report and see if we can determine what might be causing the problem and see what type of drive you have.

When you rebooted normally was the problem still there?

See if this workaround will work: don't put the Mac to sleep, just sleep the screen.

Absolutely not. It's considered to be akin to malware by most of the experienced users here. You should uninstall it according to the developer's instructions. The same goes with any A/V, optimizing or speed-up software

There is no reason to ever install or run any 3rd party "cleaning", "optimizing", "speed-up", anti-virus, VPN or security apps on your Mac.  This user tip describes what you need to know and do in order to protect your Mac: Effective defenses against malware and other threats - Apple Community   

Yes, particularly if your boot driver is an SSD.