MacBook 12inch overheat and slow startup

Thanks for the report. Here are my observations/recommendations:

1. Your notebook's battery needs to be replaced.
2. Combo Cleaner - Macs do not require any type of Anti-Virus or "cleaner" apps. I suggest that you completely remove Combo Cleaner from yours.
3. RAM Swap Used - At the time of the report, your notebook did not have enough system RAM to hold all the apps/processes that were running and needed to swap out to the system drive. This slows overall system performance. Try running fewer apps concurrently. If you use Google Chrome, try an alternative web browser, like Apple's Safari, or if you really want a Chrome-like GUI, try the Brave browser.
4. Follow the suggestions in the "Clean up" section to remove the unnecessary files.
5. The "Diagnostics Information" section is identifying that the SpeechRecognition process is using a high about of %CPU. When this happens, the overall system performance can be reduced. You can also see the negative results of the Combo Cleaner app has on your system. For now, I would suggest ignoring the trustd process high CPU usage item. This process is part of macOS and was made available with the release of Sierra. This is a daemon that runs in background that manages and checks certificates for all processes on the system.

FWIW. WindowServer is a core part of macOS, and acts as a liaison between your applications and your Mac's display. It is a part of Core Graphics. WindowServer gathers in images of each of the windows in the system, assembles them into the composite image which will appear on the display, and passes that onto the GPU and display system.

I suggest that you run an EtreCheck report to see if there is something else going on with your notebook. EtreCheck is a diagnostics tool. If you need assistance with interpreting its results you can post them here.

Ref: Using EtreCheck to Troubleshoot Potential… - Apple Community