Hi Gabriella and welcome to the club!
Hope this experience isn't making you have any regrets. Fingers crossed it will be something quite simple like in the video that Dec put up, maybe you could show it to the dealer and they could check the switch out?
I've owned numerous Lexus models over the years and like you recently purchased a IS250c my first ever convertible and I absolutely love it! Only problem I've had since buying it is waiting for the rain to stop!
Please let us know how you get on.
All the best,
Tony