Then I've got good news for you, using a nightly build will make anything you do on your mobile faster. To install it just read the instructions at https://wiki.mozilla.org/Mobile/Platforms/Android#Download_Nightly. The speed difference is very, very noticeable - worth installing.
Can you enable telemetry on your device and the error console and file a bug and paste the startup numbers from the error console in that bug ?
Way the app is packaged , and that changes startup time very nicely for me at least.
Seems to be hardware dependent much.
Nightly on my S2 flies. (nearly instant startup, very smooth browsing)
Nightly on my tab10.1 sux so bad (5s startup, choppy choppy choppy and more super choppy experience)
What's changed?