How to Initiate A Blowjob

My man seems very insecure with himself. He has no hesitancy when it comes to touching me but, every time I try to return the favor, he won't let me. I want to please him the way he pleases me but I don't know what more I could do without tieing his ass up and just going for it. Any suggestions in making him feel more comfortable so I can get this show on the road?