There are two factors that will affect the SNMP trap when SPX boots up.
One is the SNMP function must start, and the other one is the network must be ready.
If snmp is off, SPX will not send trap. If the network is not ready, trap will not send out.

When SNMP starts, the SPX will send "cold start / warm start" trap. When the network is ready, the SPX will send "Link up" trap.
Since SNMP starts before the network is ready, only the "Link up" trap is sent, and cannot send "cold start / warm start" trap.