You can sue anyone, at any time, for any reason.
Patent lawsuits, especially IP patent lawsuits, are for dicks.
Don't be a dick.
The entire wording of this question is focused on the future ability to sue competition which may never exist, or which would otherwise beat the pants off your startup because while you were focusing on patent trolling your industry, they were actually making products and services people wanted.
That said, is it "worth" getting the various bits of "secret sauce" of your startup patent-protected whenever possible? Maaaybe! The cost and time sink may well pay off if you have a particularly complex hardware solution, or even more complex software algorithms working together in a wholly unique fashion.
To your followup question: once you "go active" with your desire to sue infringers, all the competition and even some of your less-patent-friendly customers may start looking into prior art – that is, instances of your technology/algorithm/feature that existed before your patent was awarded. You may still certainly sue anyone who qualifies as pre-existing, but it will be a much harder case to win, and it will basically be a race to see who runs out of funding for litigation first. Good times.
Does getting a patent on your startup idea means you can instantly sue any clones out there?