Although the browser does accumulate garbage which needs to be
cleaned periodically, which does require more effort on the
browser's part to reclaim that memory, I can't confirm pretty much
any of what you mention -- certainly not five minute pauses. I'm
typing this reply to you in 38.4, after all.
A fresh user profile would, indeed, dump pretty much everything
except your bookmarks -- in fact, that's the whole point, to start
from a known state. You do have a lot loaded into the browser, and
if you have settings altered in about:config, you may have put the
browser into an unsupported or untested state. If you want to try
as a last-ditch effort, the instructions are to the bottom right
under "How to reset your profile." If that fixes the problem,
either your addons or custom tweaks were to blame. At that point,
since you know exactly what addons you're running, you can try
reintroducing them one by one.
If that doesn't fix it, unfortunately I don't really have any
other suggestions for you based on your description. Generally "the
browser is slow everywhere" isn't something I can offer much
assistance with because the symptom could have any number of
causes, a substantial amount of which are specific to the local
machine. If you're running Leopard, you could try Leopard Webkit
and see if that serves you better.
Okay, I had forgotten about the reset procedure, as I had never found it necessary. Also, I neglected to specify that I'm running OS X 10.4.11 (hence the "TenFour," yes?).
So, I did a complete wipe, and re-installed a bare minimum of privacy add-ons. I'm seeing marginal improvement, but it's still dead-slow when compared side-by-side with an ancient winbox running Firefox 42 on Windows XP final. Contextual menus are working much better, but the longer my session runs, the slower TFF is at page rendering and recovering from tab switching & closing.
Bottom line: I think the web and modern browsers -- and any reworked version thereof, such as TFF -- are simply becoming too bloated and script-dependent for our poor old PPC machines to handle with any reliable fluency. Unless there's a way to make it less bloated...make it work...ON PPC. After all, we are kind of counting on that, or we wouldn't be here.
If you're running TFF on an Intel machine and/or a newer version of OS X, well, goody for you -- but that's kind of beside the point & original stated purpose of TEN-FOUR-Fox, isn't it?
Just an observation. I don't think anyone here is threatening to sue just because their free download doesn't fetch their slippers and serve them frappuccinos every morning. Right?