Users of older generation 'Haswell' and 'Broadwell' Intel CPUs are reporting of constant reboots after applying patches to address the Meltdown and Spectre vulnerabilities. Intel is looking at issuing a revised firmware to address specific issues related to these CPUs.
https://www.notebookcheck.net/Intel-Haswell-and-Broadwell-CPU-users-complain-of-higher-system-reboots-after-applying-Intel-s-security-fixes.278212.0.html