My Mac memory is full. I can’t start the computer. What do you recommend?

Rather than suffer a reinstall right out of the gate, Try booting into Safe Mode:

How to use safe mode on your Mac - Apple Support

Safe mode load fewer files and MAY let you get a workable desktop, from which you can delete files or move large ones from your internal drive to an external drive.

You mean your Mac storage on the boot drive, right?

EDIT.

Boot into the Recovery volume (boot with the Command + R keys held down  - Intel Macs) or  (How to Boot an M1 Mac into Recovery Mode), select Disk Utility and check as to how much free space is on the boot drive.

Post back with the results.

What is happening when you wait? Will it not boot?

You can press cmd+r at startup to go to macOS recovery and reinstall macOS. If you don't have a backup it is possible that you will loose files during this process