Unless your B17 Pulsar has the optional manual transmission fitted, then it definitely has a CVT. The reason Nissan (and many other carmakers) still use the old PRND symbols for the gearshift are because that’s what people understand, so there’s no confusion.

In any case, even though it’s a CVT and not a conventional automatic, the CVT still has a Park position, a Neutral and both a Drive and Reverse position, so the symbols are entirely consistent with that anyway.

A modern engine like the one in your Nissan uses electronics to control the ratio of fuel and air, rather than a physical choke like older engines use. However, in order to control this ratio, the modern engine relies on a range of sensors dotted around the car to tell it what’s going on. Examples include a throttle-position sensor, ambient temperature sensor, coolant temperature sensor and many more. If just one of these sensors fails or starts relaying false information, all aspects of the car’s running (including its throttle action) can be compromised.

But before you start scanning the car and spending money to fix the engine flaring during gear changes, take a hard, critical look at what you’re doing with the pedals when shifting gears. If you don’t completely release the accelerator pedal during a gear change, or get your hand-foot co-ordination wrong, the engine will naturally flare during the shift. And because modern cars have a throttle-by-wire system, there’s not the same degree of feel and feedback through the accelerator pedal as some of us are used to. It sounds a bit obvious, but checking your driving style is the first step.

This sounds a lot like a faulty ignition barrel or an electronic key that has a semi-flat battery. A worn barrel can often prevent the necessary contacts meeting to complete the ignition circuit and, likewise, an electronic key without sufficient power can also give these symptoms as it struggles to enable the ignition. This can be a very hit and miss thing, which is just how you've described it.

So check the condition of the battery inside the key and perhaps the condition of the car's battery as well. If the situation gets worse, a trip to the auto electrician is probably in order. At least your STS model has a relatively conventional ignition key set-up, rather than the push-button, proximity key of the SSS model which brings another layer of complexity to this function.