Sometimes Mac Studio M2 doesn’t start

Your original post mentions macOS 15.7.3 which is a couple of updates behind. You may want to install those update patches to see if that makes any difference.

If this is indeed a PRAM issue, then you can reset the PRAM by using the Terminal command line. Issue the following command in the Terminal app:

sudo  nvram  -c

This command will prompt you for your admin user password. Nothing will appear on the screen as you type the password. Press the "Return" key to submit the password. Sometimes you may see a message that certain items cannot be cleared such as the computer name which is normal. Assuming the command actually succeeds except for not being able to clear certain items, then you will need to restart the computer so that the system pulls in the default PRAM/NVRAM settings.

One final option that I can think of trying is a DFU Firmware Revive which resets the security enclave chip & system firmware. Theoretically this should not affect your data, but I highly recommend making sure you first have a good backup just to be safe. Unfortunately this option requires access to another Mac currently running macOS 15.7+ Sequoia, or macOS 26.x Tahoe. Apple Configurator v2.19 is necessary if the host Mac is running Sequoia.....if the host Mac is running Tahoe then the Finder will work, but you may find Apple Configurator is easier/provides a bit more details.

Why I am asking about AC power:

Your symptoms match what can happen to a desktop Mac when its PRAM Backup battery has become exhausted. [That is not a definitive diagnosis, just a correlation.]

Desktop Macs have a small always-on power supply, that is used to maintain system parameters such as System Time and 'where is the boot drive'. These parameters make startup fast and easy. These parameters are important enough that a PRAM backup battery -- a 3 Volt non-recharging coin cell battery is also available, to make certain the parameters survive across power outages.

Provided you supply power to your Mac at all times, that PRAM backup battery will typically last for as many years as your Mac and be trouble-free.

If you do not supply AC power to your Mac overnight, within a few years that PRAM backup battery can be exhausted, and your Mac may refuse to start because the battery is too low and the parameters have become too corrupted.

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A common debugging step when this used to happen in Intel Mac Pro towers was simply to replace the PRAM backup battery. Unfortunately, on the Mac Studio, that is a 25-step tear-down, including removing the power supply and other components, to get to the battery.

For apple-silicon Macs, Apple says a PRAM reset is not needed, and that likely means that PRAM Reset can not be used for additional diagnosis.

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if you need to submit your Mac for service, you must sign a paper that says you ALREADY have all the backup copies of your FILES you will ever need. Especially if major components are replaced, your files are NOT guaranteed to be returned to you.

¿What is the date of your most recent backup, and by what method?

sgrhll wrote:

With 15.7.5 I have the same problem.

There maybe no way to stop the Mac Studio from starting up after a momentary power disruption.

The best way forward, is to just leave it connected to the AC power all of the time.

Then do not cycle the power on the Surge Protector or Power Strip.

Questions

- When I upgrade from Sequoia 15.7.5 to the latest version of Tahoe, will all firmware be reflashed during the process? If so, could that potentially solve the issue, assuming it is related to firmware?

I would first try updating Sequoia to 15.7.7 and then re-test.

What's new in the updates for macOS Sequoia 15 - Apple Support

About the security content of macOS Sequoia 15.7.7 - Apple Support

- And if I upgrade to Tahoe and the problem still remains, can I then conclude that it is not a software issue, but a hardware issue?

That's kind of like smashing a finger to see if it cures a head-ache.

If you are concerned about the Mac's Hardware, run the Apple Diagnostic Test.

Use Apple Diagnostics to test your Mac - Apple Support

Or check your backup and schedule a service appointment at your local Apple Store.

Find Locations

From description of your backups, it sounds like service procedures that replaces your mainboard and/or Boot Drive would not be a File saving problem for you, if it comes to that. Great -- that gives you far more flexibility.

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Re: re-install:

MacOS does not modify itself. Any MacOS install modifies ONLY System Directories. By design, user files are left un-touched.

This means you can freely re-install macOS -- right over the same or older version, with no loss of data or function.

Do you frequently shut off AC power to your computer at night, such as by turning off its power-strip?