How to remotely reboot a Linux host if SSH fails to connect?

Edit2: Thanks all for your responses! I have checked the logs, https://lemmy.nz/comment/6192604, and based on that removed tracker-miner-fs as it's a search/index tool which I don't need. No idea why it took over all memory. I'll also get a WiFi Smartplug as a kill switch. Hopefully that solves it....