Warning buzzer sounds No warning lights displayed - RX450h

[Sonorad]

I'm new to the site so my apologies if this topic appears elsewhere.

The problem. Intermittently the warning buzzer sounds. There is no associated warning light /icon displayed. It happens  at very irregular intervals. Sometimes weeks pass without an occurrence.  Previously it occurred immediately after setting off. Today it occured after 20 minutes driving. I check all the usual points. Doors, seat belts etc. No effect. If I turn off the engine and restart the warning buzzer stops. The car has had three main dealer services since I bought the car in 2015. Nothing ever reported that points to a fault.

I will be grateful if anyone who has experienced a similar problem will point me to a solution.

 

Or should I take it to my dealer and get a diagnostic check?

 

Thanks in anticipation

Edited July 29, 2018 by Sonorad
typo