Motor not starting up

Engine Mechanical problem
2004 Nissan Sentra 4 cyl Two Wheel Drive Automatic 52000 miles

My car has had significant starting problems (May take a few minutes to start, especially when cold outside) then will idle very rough for 5 seconds or so and die if I don't push the gas pedal most of the time. I know others have had this problem but im not sure if its the fuel pump regulator or the crank sensor problem or someother problem. While driving at slower speeds and sometimes idling, it also makes a sound of liquid passing through the engine.
I notice this problem to come about in mornings and when I take it to work and let it set for 5-7 hours.

Yes the check engine light turns on sporatically, it is not on at the moment. When starting it doesn't go beyond 1500 rpm unless I push the gas pedal.

A few months ago I had my car checked by a mechanic who discovered the codes and supposedly cleared them. This turned off my check engine light for less than 50 miles and then it turned right back on. I will follow up with the mechanic and find out the codes. Thank you

Cranks but will not start I have changed both crank and camshaft shaft position sensors with no luck. It is not getting any spark at all what could be the problem and how do I fix it? Thank you

The vehicle has a passlock system on it and a regular old key I have tried just about everything and I have cleaned both the battery terminals as well as the connections

Have tried the key trick and of course did not work and I have had it scanned but it is not show any codes I have even pulled both the coil packs on each plug and the plug to check for spark and no spark at all.

I had a mechanic do it and sat there and watched him and looked at it as well

2004 Nissan sentra- intermittent starting problem.
Ongoing problem- sometimes all it takes is moving the car forward a few inches, or slamming the door and it will start. Once it even started right up after just sitting for a couple hours.
All other power is on.
The engine does nothing, no cranking at all. Note- with key turned on, the car will not go into neutral.
Most of the time this car starts right up- today we can not get to start at all. Any ideas? Appreciate any help you can give.

We recently bought a 2004 Nissan 1.8L, its always had a delay (on occasion) with starting-it tries to crank and you have to turn it off and try again and it starts.
It hasnt been a big deal since its always started (the previous owner said it was when the AC is on but I noticed it with or without).
Recent issue is that the car wouldnt crank at all, no click, nothing. We cleaned the acid off of the battery posts/cables and jumped the car. It ran fine for a couple of days. Then again, it stopped starting. We replaced the alternator and jumped the car, turned on the AC and the lights dimmed and turned the AC off and back on and it died, tried to start the car, it just clicked. (Sometimes it clicks, sometimes it does nothing) The only way to start it was to jump it. We got a new battery, same thing, only jumping it would start it and it was having problems cranking (took a loooong crank to start). We drove it and it died while foot on gas. Jumped it again to get it home, made it a mile and died again.
Please help! What else can we check?

The alternator reads at 14.5ish, it stays steady, the battery is the same unless the car is running, it drains when it is connected to car. When reading it, it was slowing decreasing, this is why the car dies after driving it for awhile (we just figured out). Any idea's what to look at? I super appreciate all of your help!

Thanks for all of your help. It was the positive battery cable post. Replaced the tip of it and car started right up and kept the charge.