Mar 11, 2018 - 2:25 PM
in reply to Hamza
The weatyer may have some cool tips. ;-)
September is usually considered the best month for traveling in Switzerland. The August rush of tourists has pretty much dissipated, and the weather is at its best.
By the time you get into October, there is increasing chance of snow at high altitudes, and by late October, there is a high probability of snow on the higher Alpine trails.
Since I assume you will not be doing much hiking, that should not present a problem.
Mountain passes usually close in December, sometimes earlier, but there can be occasions where they close much sooner:
The last of your route, back to Interlaken from Geneva does not require high altitude driving. I'm not sure about the roads from Nice to Geneva, but some are mountainous.