Hi Mandar,
I just did a test, on my end, to see if I can produce the same results. This is what I've got:
From SIA start to DB connection - 17 seconds
From SIA start to CMS startup - ~3 minutes
From SIA start to complete start - ~10 minutes
In doing this, looking at your issues, I would peg this up as a resource issue. I'm not sure if you've split up the APS or not (As I've only split up into 4 different segments, considering I'm only running with 8GB of memory), but that can help improve performance.
The shops that I've been apart of, getting Wireshark installed is basically near impossible. Thus, I've never gotten a chance to see exactly what information is pulled from the database to the BI app server. For me, I'm a stickler to knowing every little nuisance about the application, it helps me get a better overall understanding of the application, and where to best look for information.
As such, if you're shop is more lax than the ones I've been, and am, apart of, I'd suggest trying to do 3 different things. Either install Wireshark on the BI app server and see if anything of use is displayed within it, as far as latency goes. I would also recommend working with the network folks, so they can monitor the various devices between the BI app server and database. There might be a latency problem between those two that are unforeseen, unless you have direct access to those hardware.
If nothing comes out of that, try to split the APS, if you haven't done so, and/or increase the amount of memory that's currently on the server itself. From there, allocate that extra memory to the various services to help improve performance.
If the problem still persists, please post up your findings for the above and I'll continue to give you a hand. Thanks,
-Victor