Okay, I one-hundred percent used to act like this for several years, so I can explain this and the mindset behind it, I think. I hope you see this.
What is speaking here is a lack of confidence. The lack of dating experience isn't really the problem. I can tell you right now that an un-confident man isn't an easy problem to fix, but once you've fixed it or learned to deal with it you've found a keeper.
Basically, these types of guys get a lot of self worth by how much people that matter to them treat them, because they've usually gotten it in their heads that they aren't worth much from past relationships. At the beginning of the relationship, you've basically got to make sure you give him a lot of attention and affirmation. Compliment him and let him know that you've been thinking about him if you haven't seen him recently. This can also be replaced by occasionally just making a point when you're together to tell him how much he means to you. We insecure dudes need that.
However, I know a lot of girls don't like an unconfident dude and I can definitely understand. We can be very taxing, with always needing to be reassured and all. I can tell you though, from my case and from close girl friends of mine that have dated shy dudes, that once you overcome this unconfidence problem with them and convince them that you are 100% really, truthfully into them they tend to be some of the sweetest people ever. They've been put down enough in their life to not want to inflict that on other people. I guess I can't say this goes for all insecure dudes, but I know a good amount of them myself (as a former really shy, un-confident dude) and this generally seems to be the case.
This type of guy will always come with a unique set of struggles like all types of people. They get hurt easily by sometimes small and insignificant things. They are probably a little more needy than your average guy.
All in all, wanna help this guy you are dating? Just tell him to relax and that you care about him fairly regular. Sit him down and let him know you understand. Eventually that confidence will appear.