My Mac randomly shuts off. IS it a battery issue or a software issue?

If it only happens when using the laptop on battery, there is a good chance the battery is at fault. If it occurs when using the power adapter, then it is unlikely the battery is at fault.

Try booting into Safe Mode to see if you have the same issue. If you don't have the issue while booted into Safe Mode, then most likely the issue is due to some third party app you have installed.

Make sure to disconnect all external devices in case one of them is causing a problem.

You can also try running the Apple Diagnostics to see if any hardware issues are detected. Unfortunately the diagnostics rarely detect hardware failures.

Do you have the Intel or Apple Silicon version? And what version of macOS are you running?

Writing an effective Apple Support Communities question

There is very little actionable information provided to even begin to Guess.

Reliable , accurate, details / context will really help and as it there is very little actionable information to work with.

What has the User ( you ) done to try and fix this issue.