Force the next boots into Safe Mode (and back) — via Microsoft Learn

The easy way

1. The easy way: press Win+R, run msconfig → Boot tab → tick Safe boot (Minimal, or Network for internet) → OK → Restart. Untick it later to go back.
2. One-off alternative: Advanced startup → Troubleshoot → Advanced options → Startup Settings → Restart → press 4 or 5.

Command

Run in an administrator Command Prompt / Terminal window.

bcdedit /set {current} safeboot minimal

Undo

bcdedit /deletevalue {current} safeboot

Use safeboot network instead of minimal if you need networking. Write the undo command down first: the PC keeps starting in Safe Mode until you run it (if Windows won't start at all, run it from Advanced startup → Command Prompt, where {default} may be needed instead of {current}). Microsoft notes BitLocker may need suspending before changing boot settings.