Can you please take the thread dumps (2-3) between that time so that we can identify the cause of this.
you can upload the complete .out after taking the TD to some external site and send the link.
If weblogic seems to load slow, or connecting to the nodemanager takes 4-5 mins, the issue may be with /dev/urandom
Note that the /./ is needed.
I know this seems odd, but it fixed the 5 min startup issue that we saw.
I hope this helps.