why wont my car start?

a couple weeks ago my car wouldnt start when i tried to go to work, it just
clicked once every time i tried. tried jumping it, didnt work. battery gauge is
normal. replaced the starter, didnt work. cleaned up wire connections,
replaced
a ground wire, and had a new ground wire installed on the starter. none of it
worked. randomly it started working again until a couple days ago the same
thing happened. looked up some things, saw online someone say something
about the engine immobilizer so i followed the steps that i found to see if that
was the problem. it started right up after doing that. making me think that is
the
issue but reading into it more, it doesnt seem to be acting like others are
saying if thats the problem. theyre saying itll keep cranking and wont turn over
or itll start and shut right off and that the gauges wont work but mine wont
crank and the gauges are fine. it again, wont start even after following those
steps again. im wondering if anyone knows of any other problem that could be
causing this or if it definitely sounds like the immobilizer.

i also had an alternator put in almost a year and a half ago, new battery
around
the same time, and newer terminals.