So, 2018 would be an R52 series with a 3.5L-V6 (not a 3.5). If it's under 60,000 miles, it may be covered under warranty, so you should check with your Nissan dealer. You can also have the codes checked; many auto parts store will check powertrain codes for free. Crank position and cam position sensors can sometimes start to fail and cause those symptoms and not always set a trouble code.