Microwave makes strange static sound????

Hi
The microwave in my 3 year old bullet started making this strange sound when it was plugged in - not running - just plugged in. Sort of a crumpled paper, static sound that would be loud enough to hear all through the trailer and that comes and goes.

I called Keystone. They were not overly helpful. The person I talked to suggested I just have it replaced. I asked him who makes the "Highpointe" microwave - he didn't even know and sent me off on a wild goose chase calling 1800 numbers that are no longer in service. I found out eventually that it is made by the Guangdong Midea Micorwave and Electrical Appliances Manufacturing Company from the Peoples Republic of China. I am sure they will answer my inquiry with post haste as they are all about making trustworthy products and excel in customer service - won't be holding my breath.

Any ideas if this is something that could be fixed? How hard is it to replace a microwave in an RV - just take the shroud off and find a new one the same size??

Thanks for your time.