I just took a 35 mile drive on the Highway in 90+ degree weather.
Top up, all windows open, A/C not on.
On the return trip I was starting to smell fuel in the cabin, pulled over and popped the hood.
Did not smell anything in the engine compartment or see anything leaking.
Continued on then started smelling exhaust fumes in the cabin, shortly later it disappeared.
Then as I traveled back to my destination it happened multiple more times, both fuel and exhaust, once after I accelerated to pass a car the fuel smell came on heavy.
Got home and parked outside the garage just in case the car caught fire, luckily not.

Any suggestions where to start looking?
Also encountered my first Engine Coolant Low Warning, It too was intermittent.
No leaks on the garage floor or fuel smell anywhere on the car after 5 days parked .

 

check for exhaust manifold gasket leaks or cracks, then work your way down to the cats and exhaust.

 

check your fuel damper, that's where mine was leaking gasoline