2004 Toyota Corolla Automatically wipers are switching on.

I am also getting issue with my 2004 Toyota corolla LE with 115000 miles, I am looking for solution to it. As per the reply saying Specific tests to identify the issue, Can I have some details. I checked with 2 to 3 auto mechanics they are saying need to replace the switch which is going to cost me more than 300 to 400 bucks cost. I am just thinking if there is any switch issue it should happen always right, why it is happening at the time rain and snowing. Thanks in advance.