Wierd starting problem

My 2003 Dodge Dakota with 4.7 engine had for a little over 2 years. After I got it one day it would do nothing to start, starter would not make contact. It sat for a coupe of days till friend that is mechanic could look at it. Started right away. Went on about 6 months and did same thing but it eventually started same day. It is now getting where it might be once a month but sometimes truck will set for 2-3 weeks without being used. It is my machinery hauler. I have found that when a no start situation everything on dash works except the gas guage, set awile perhaps a half hour on possibly 2 hours and gas guage starts working again and it will fire right up. Yesterday drove it quite a few miles and stoped and started several times with no problems. Last time I shut it off it sat for probably an hour and a half. No gas guage movement and no atempt to make contact. tried several times in next half hour, same thing. 5 minutes after last time nothing it started as should with no problems. One time it actually was at gas pump at station. Any ideas why that gas guage would decide to not work and do nothing when key is turned and 5 minutes later start as no problems ever. It is the 2003 4.7 V8 auto 4 wheel quad cab. I had a 2000 extended cab auto 2 wheel drive and it never acted like this nor the 2001 3.9 6 cylinder regular cab 2 wheel drive I also have now and use when it is big and powerful enough for job. Could that be a computor failing on just part and if so where is the computor located on the truck. Friend that is the mechanic had no idea. Getting so I cannot trust it. The radio did not work when I got the truck and in no start have not tried headlights or heater fan. It is not the battery and I have tried a jump start when it would do nothing with the jump doing nothing.

Does it show any codes? My 2008 did the same thing,never knew when it would leave me sit. After numerous trips to the dealer with no results,it finally threw a code... "does not recognize key" factory anti theft program. Tried a new remote with no success. dealers fix was to replace the (ecm $1600)I passed on the new ecm and wired in a push button. Now if it won't crank,I turn the ignition on and hit the button...starts everytime.

My son bought a F150 van with the same problem. The ECM has a crack in it so in hot weather it expands an no start, Put a starter button on it and no more problems

Have you tried running a wire from the battery to the starter during the time that its not starting regularly? Could help narrow down the issue

Finding an intermittent electrical problem is the worst!

I found you can go on Auto Zone, sign up for an account, and access wiring diagrams for "most" late model vehicles.

If they have the diagram, search out the start circuit, see what the gas gauge has in common with the start circuit. Also, next time it does it, look carefully for any other accessory that is not working. That will be a place to start, but then a matter of catching it in the act.

Another thing to do, look for Dodge Dakota forums, customer service/complaint listings, factory service notices, etc. Look for a common thread, others that have the same problem and what the solution was.

Youtube sometimes has some solutions.

When problem is there, is the check engine light illuminated? What does the odometer read, correct mileage or "no bus" ??

A couple things here.
First, if the CHECK ENGINE light (or icon) does not light when you turn the key to the ON position, then the engine computer is not getting power. Whether that will prevent the starter from operating, I do not know.
Second, is there anything else besides the gas gauge that does not come on or operate when it is acting up?
Third, the engine control computer is located on the inside of the passenger side inner fender.
Fourth, have you checked the condition of the battery terminals? Are they corroded? Clean and tight? Ground wires? Firmly attached and clean and tight?

Lastly, if it turns out that you do need a computer, I will post you the name of an outfit that will sell you a rebuilt for a very reasonable price (with exchange) and give you a lifetime warranty on it. The last one I had a friend get cost him around $150 exchange for a Jeep Liberty.

Try turning the key on 3 times in rapid succession. Turn it to just before it would turn over. Then watch in the mileage window for any codes that show up. It will run 2 sets of them before it is done. Get back with the numbers if any and I can tell you what it is saying.

Cannot even get under the truck to see the starter. Trying to get ideas to talk with garage about things.

There is a good reason why most parts stores usually have a half a dozen ignition switches in stock for your truck.

Not expensive and not a hard thing to change, I have replaced quite a few of them to cure the symptoms you described.

How does the switch only afect the gas gage and starter and not all the lights that come on before you start engine for system checks?

Have not thought about checking that.