Is it true guys are intimidated by shy girls?

HELL NO! I find shy girls rather annoying, to be frank. I'd like to have a conversation that consists of more than "yup", "i dunno", or my personal favorite "we can do what ever you want to do"! I look for outgoing for no other reason than to have good conversation.
you can't make plans for 2 with only one opinion, in my books.

I was painfully shy when I was younger, so I can relate here. While it may be difficult to break out of your shyness and be more outgoing, you will definitely be better off socially if you do. More people will want to talk to you and interact with you if they think they can approach you.

People are put off by shy people because often the shyness is misconstrued as aloofness or snottiness.

Horrifying - I know. I used to be a shy guy and was shocked when I learned so-and-so thought I was aloof. WTF! So then I worked on eliminating my shyness.

Guys are going to be scared off by the shy girl. They'll think you don't know they exist.

So, even though it's really hard, you need to get over your shyness. It doesn't even have to be with guys at first! Strike up a conversation with a random person you meet on the bus or in class. (Ask them their name if you don't know it, and ask them an open-ended question about something you have in common, like a class or teacher. Don't let the conversation fizzle out. If they mention something they're interested in, ask them about that.)

Eventually this will make it easier for you to get over your shyness. Plus, when guys see you having conversations with other people they won't think you're so intimidating.