We
purchase several Dell Micro Optiplex 3070 and install on KE, we found the Dell
cannot bootup sometimes while another PC/Server work fine, do you have any fix
for the issue?

Please
upgrade Dell 3070 BIOS to latest v1.1.3 and the issue can be fixed.

https://www.dell.com/support/home/uk/en/ukbsdt1/drivers/driversdetails?driverid=tdrwk&oscode=wt64a&productcode=optiplex-3070-desktop