I just put servos in my truggy and when I turn on the switch they make a buzzing sound, any thoughts on what this could be caused by?

What brand? And it's normal thing with digital servos

There solar servos, just something cheap to get the feel of the truggy while I break in the engine this spring then I will put something better in. They are digital.

some but not all servos do this, if they are working properly i wouldnt worry about it.

You should be alright I have savox and spektrum servos and there really loud

They do seem to be working fine, I was just worried they might be bad since its so loud but if its pretty common then I won't worry about it.

I used solar servo's for a year in my 2wd, good servo for the price. It is digital and normal. My 22 and 22T both did this, no issues