New to me 370z roadster and overall questions

RM0911

Hi everybody,I recently got a 2010 370Z Roadster Touring AUTO trans with 22k miles.
I`ve encountered some "problems"(not sure if they are) and come up with some questions as well hope you guys can help me out.English is not my first language, please bear with me .

First thing I`ve noticed is the sound comes from the bottom of the car .I can hear it every time when i park my car and it lasts around 4 minutes. It sounds like rain drops hitting the metal roof or something is being fried in the oil or small stones hitting the bottom.(I`m trying my best to describe it lol)
I have no idea what it is and why does it make such sound, anyone has encountered this before?

Second thing is that when I come to a stop the steering wheel turns itself little bit . It`s not such a pain in the *** just wondering why is it happening? Because I`ve never had this before on my previous 11`mustang and 13`FRS.

I`ve been reading some threads from other users and one thing I worry most is the steering wheel lock.I definitely don`t want to pay $1k or more for this and I want to fix it before it happens.After compared with several methods I `ve decided to go with this steering wheel lock harness :Steering Lock Harness - Car Kit Company
Has anyone used it ?Does it work well?

Last but not the least is the roadster`s top issue.I`ve read some threads their tops are either broken(wears,holes) or not functional(cannot open or close). I`ve also heard it takes $7k-15k to fix which is totally unreasonable.I`ve ordered Raggtopp Fabric Top cleaner/protectant kit and I want to ask if there is ay tips and advices how to maintain and use the top properly? I`m expecting to use this car for at least 3 years.

370Z is definitely a great car and driving with open top is definitely a pleasure.i `m really happy to join the 370Z family and hope you guys can help me out with my questions.

Have a good day!