very strange, you need to work the shifter and have someone under the car check the arm on the trans is moving as you move the shifter,
if all is well figure a v body fault or the trans needs to come out for a rebuild reseal,
My car would refuse to start in Park when hot and not quite go into gear quite right sometimes.
I re-routed the cable and insulated the part near the exhaust as I realised that heat effected the length of the shifter. Therefore the selector lever position.
It was much better after I had re-routed and insulated it.
I could get all the gears even when hot. But still just occasionally I couldn't start the car in Park. No big problem because I just shifted to Neutral and started it there.
But also I don't think the gear selector lever that came with the shifter is quite right.
I think the hole for the cable end is in slightly the wrong position. Which means the reach of the lever is altered.
When things start working differently the first thing you do is look at what has altered.
Standing in traffic shouldn't have any effect on your transmission function.
Or buy yourself a Kawasaki H2...it would be safer!
A better animal was the H1, handling wasn't in their dictionary When the center plug wasn't fouled & motor was running well, then that was one hell of a ride
Hard to believe they followed virtually with the Z1
"I spent a lot of money on booze, birds and fast cars. The rest I just squandered."