Altima wont start

I have an 05 Nissan Altima 2.5 S auto with
159k miles on it. It sat for about a year. I just
got it back from the shop after some
exhaust work. The next day my wife drove it
20 miles to a store. After shopping the car
would crank but not fire. She let it sit for
about 30 min then it fired up and ran fine.
She made another stop and again it wouldn't
start. Waited 30-45 min it fried right up and
ran fine. The next day same problem. My
mechanic said must be fuel pump. I installed
new pump and it fired right up and ran fine
for 2 days. Today she took it to gas station
15 miles away and it wouldn't start after fill
up. After about an hour it fires right up and I
drove it home. When I get it home I shut it
off and restart it 5 times with no issue. When
it starts it runs perfect. The only other thing
I've done is swap fuel pump relay with
another and it didn't help. My mechanic says
now he thinks it's the ignition switch. I'm not
convinced. I'm not going to keep throwing
expensive parts at it hoping for the best.
Can anyone help me?