There's indeed an issue with SD cards in current ESXi versions. However, that may or may not be the reason for the reboots. ESXi usually stops with a PSOD (Purple Scree Of Diagnostics) rather than rebooting itself on errors.

1. Please check the Dell server's iDRAC logs for related entries
2. ESXi always runs on UTC. The displayed time gets adjusted (for most screens) in the GUI depending on the client's time zone.
3. What exactly is it that shows the high utilization? The ESXi host, a single VM? Please provide some details.

André