What are problems with my Mac that I can detect early on?

 Problems with your Mac that you can detect early on:

• Restarts that occur frequently and unexpectedly-Kernel panics are sudden and frequent restarts, especially when accompanied by an onscreen warning. When your computer reboots, you'll frequently get the 'Your computer was restarted because of a problem' error, which is Apple's counterpart of Microsoft's Blue Screen of Death.
• App Crashes and Freezes-There are a variety of causes for these problems, although some are more common than others. Low disc space is a common cause of performance concerns, especially when your Mac is awakened from Sleep Mode. Memory and storage problems, or simply a machine that takes on more than it can handle, could be to blame.
• Battery Life Is Shortening-They all show indications of ageing over time. For instance, your device will not last as long on a single charge, and it may not even hold a charge at all. There is one obvious course of action in this scenario, but it isn't the only option.Problems with the System Management Controller might potentially cause power issues (SMC). 

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