Hello,
I have the same problem with 4.4.35-1-pve version, the system reboot when I launch a third VM
Hardware : Dell
CPUs : 8 x Intel(R) Xeon(R) CPU E3-1230 v6 @ 3.50GHz (1 Socket)
Kernel Version : Linux 4.4.35-1-pve #1 SMP Fri Dec 9 11:09:55 CET 2016
PVE Manager Version ...