A
"CleanMyMac" is a scam and a common cause of instability and poor performance. Depending on what version you have, the developer's instructions may not completely remove it. Follow those instructions, then do as below.
Back up all data before proceeding.
Triple-click anywhere in the line below on this page to select it:
/Library/LaunchDaemons/com.macpaw.CleanMyMac2.Agent.plist
Right-click or control-click the highlighted line and select
Services ▹ Reveal in Finder (or just Reveal)
from the contextual menu.* A folder may open with an item selected. If it does, move the selected item to the Trash. You may be prompted for your administrator login password.
Repeat with this line:
/Library/PrivilegedHelperTools/com.macpaw.CleanMyMac2.Agent
Restart the computer and empty the Trash.
You may also have to remove one or more of these items in the same way:
~/Library/LaunchAgents/com.macpaw.CleanMyMac.helperTool.plist
~/Library/LaunchAgents/com.macpaw.CleanMyMac.volumeWatcher.plist
~/Library/LaunchAgents/com.macpaw.CleanMyMac3.Scheduler.plist
Never again install "CleanMyMac" or anything like it.
*If you don't see the contextual menu item, copy the selected text to the Clipboard by pressing the key combination command-C. In the Finder, select
Go ▹ Go to Folder...
from the menu bar and paste into the box that opens by pressing command-V. You won't see what you pasted because a line break is included. Press return.
If the problem isn't solved, continue.
B
When you see a beachball cursor or the slowness is especially bad, note the exact time: hour, minute, second.
These instructions must be carried out as an administrator. If you have only one user account, you are the administrator.
Launch the Console application in any of the following ways:
☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)
☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.
☞ Open LaunchPad and start typing the name.
The title of the Console window should be All Messages. If it isn't, select
SYSTEM LOG QUERIES ▹ All Messages
from the log list on the left. If you don't see that list, select
View ▹ Show Log List
from the menu bar at the top of the screen.
Each message in the log begins with the date and time when it was entered. Scroll back to the time you noted above.
Select the messages entered from then until the end of the episode, or until they start to repeat, whichever comes first.
Copy the messages to the Clipboard by pressing the key combination command-C. Paste into a reply to this message by pressing command-V.
The log contains a vast amount of information, almost all of it useless for solving any particular problem. When posting a log extract, be selective. A few dozen lines are almost always more than enough.
Please don't indiscriminately dump thousands of lines from the log into this discussion.
Please don't post screenshots of log messages—post the text.
Some private information, such as your name, may appear in the log. Anonymize before posting.
When you post the log extract, you might see an error message on the web page: "You have included content in your post that is not permitted," or "The message contains invalid characters." That's a bug in the forum software. Please post the text on Pastebin, then post a link here to the page you created.