Engine shuts down every 15-18 miles ,used to be every 40-40 and before that 60-70 ,wait 10 minutes & it restarts

Bad ignition module heating up and failing.

Fuel relay is what I would look into next. Check the temp of the vehicle to when it shuts down.

What was the code you got,after the sevice soon light came on,and you had the code pulled?

Check the fuel cap!! If the vacuum relief is not working it can impede the fuel flow and cause the engine to shut down or not restart after a stop. Waiting usually gives things a chance to stabalize and the engine will restsrt. When this happens again try loosening the cap and see if the engine will restart.....If it restarts immediately, REPLACE the fuel cap..Do Not leave it loose because this will cause other problems. If it is not the fuel cap the problem may be the filter, the fuel pump, or aome other fuel system malfunction.

you need to have car scanned for codes and it sounds like it is due for a major service

Do you get a check engine light? If so, read the codes with a scanner and chase down the clues. Does the PCM match the car and engine? Was the original engine a 3.8L? 5 to 10 minutes is not very long for an engine to cool down appreciably. Hopefully, the PCM codes will indicate whether the missing problem is fuel or ignition related.

I would suspect a faulty EGR valve, but is the check engine light on? If it is, take the vehicle to an autoparts store and have them use a scan tool to retrieve the fault code(s) stored in the computer. Most parts stores offer this service free of charge. That will narrow the search for the problem. Sure hope this helped.

change ur fuel pump ,

Well 145K is alot of miles, catera's are not that reliable especially after 100K. It sounds like you could have multiple issues but take it to a mechanic asap before it becomes unfixable.

It could be something as simple as a bad or loose ground wire but the hard part is finding it.
Good luck
Sam