I saw a very similar issue on ESXi 6.7, RHEL8.5. I have 16 VMs running, some of them reboot randomly. If I keep them running long enough, I think all of them will go through reboot. When I first create all 16 VMs and bring them up, almost every time 1~3 of them will reboot just after the first-boot (cloud-init was terminated). I couldn't see anything from guest VM's log, and this can happen on different VMs or hosts. I have the environment ready, it is easy to recreate this problem. I can provide anything can help with this issue when needed. Thanks.