Use vm-list to determine the name of the vm you want to start
[root my-xen-server-box ~]# xe vm-list
uuid ( RO) : 60c1607b-1e51-bfe7-088e-a4a868b80f7f
name-label ( RW): docker
power-state ( RO): running
uuid ( RO) : 96b5c2e3-5c76-a354-74ef-c324069a7c91
name-label ( RW): jenkins
power-state ( RO): running
uuid ( RO) : e0bac120-5676-50fc-7989-c11f5cf1537d
name-label ( RW): puppet_host1
power-state ( RO): running
uuid ( RO) : cc502056-ee19-1c97-a90c-a6dfe766db67
name-label ( RW): devops
power-state ( RO): halted
uuid ( RO) : c4555386-c498-4434-8926-3a42e607aabc
name-label ( RW): networkadmin
power-state ( RO): running
uuid ( RO) : f312e45d-506e-a626-5b28-ba9a179f5524
name-label ( RW): webserver
power-state ( RO): halted
uuid ( RO) : dc50cbba-ec9f-4fba-8135-d104a4dc0c61
name-label ( RW): Control domain on host: xenserver
power-state ( RO): running
uuid ( RO) : e4177291-c3e8-8f6c-93ad-a127fe4e9b62
name-label ( RW): puppet_host2
power-state ( RO): running
uuid ( RO) : dbe265c4-a19d-8211-eb57-161359509a2c
name-label ( RW): puppet_master
power-state ( RO): running