Sometimes when I try to start my 2004 Titan it just clicks (like a bad connection) and then it starts up fine and no other problems occur...baffling!!

Thats normally a sign of bad connection on battery terminals friend.

Try undoing them and taking them apart to clean up the battery posts and cable connectors then reconnect tightly.

What happens is the bad connection wont let a LARGE current throgh, So when you turn the key, all you are hearing is the little solenoid trying to send large current to the starter motor which is not happening.

It is a simple and VERY cheap job.

Sometimes batteries corrode internally and short out, especially in hotter climates. When this happens it will not take a jump start no matter what. Get the battery tested and replace it if bad.

Sounds like you have a potential problem starting with either your starter itself or the starter solenoid...

start relay goes bad.

Well first of all, who ever gave you the idea of using ether to start your Titan should be strung up to the rafters and shot with frozen paint balls. Using ether to try to start this vehicle can lead to the heads separating from the block. Do not tell the dealer that you did this!!!

Is the fuel pressure ok? Do you still have spark? Its possible that a cam position sensor is not responding/relaying a signal.

is the battery swollen on the sides or front(bulge) bulging batteries = dead cell
= new battery

how many miles does it have , sounds like a rod bearing is bad or has turned , get the knock diagnosed to make sure

try new plugs

Try checking your battery and or starter. If not them you might have another electrical problem.

Where do you hear clicking noise? perhaps faulty start relay? Double check all connections are tight, especially grounds.