Try running this: journalctl -u systemd-logind -f
That will show messages logged by logind, for example: Oct 23 23:30:10 darkstar systemd-logind[733]: Lid closed. Oct 23 23:30:12 darkstar systemd-logind[733]: Lid opened. It should also log if it thinks a suspend key is being pressed. It's possible this old laptop has a screw loose somewhere and is generating spurious events. -- see shy jo
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