My Speakers switch to Mono some reason?

It weird, but sometimes when my computer is turned on, only my left speaker is putting out sound. But, I do feel a little vibration from the right speaker. Although, sometimes I turn on my computer and it's working fine.

Keep in mind that these are EXTERNAL speakers from Logitech that are hooked up to my Lenovo Laptop.

Does anyone know how to fix this problem? Listening to music isn't as awesome.

If its a hardware problem(something wrong with your speakers connection or internal problem) there isn't much I can help you with. If its not then download latest audio driver (if you mention the laptops model number ill give you a link) or if you have realtek drivers (in windows 7/8/8.1)
1 take control panel
2 type realtek in search box (most common audio driver)
3 then open realtek audio manager
4 and make sure your "main volume" is set to the center "0" and make sure your speaker config is set to stereo
5 then click the speakers to test both

if this does not work then "probably" your speaker is fried