Sounds like there's a lot of tension and muscle in your bowling. A rare case, almost like Charles Barkley and his golf swing. Are you a 4 or 5-step? The big thing with physical issues is practice. You have to rebuild a muscle memory and if the trouble is in you first step then practice that. Think of the body as a machine. Throughout the years your body has built a memory on what it has to do to get to the line. Through your layoff, rust has formed in the machine so you have to fine tune it to get it back in working order.

So the first thing you would do is find a reputable coach that can work with you because they would be able to physically see you and make educated changes. Second schedule as much practice time as possible. The more you practice the right things the better you get. Third, sounds silly but take a Nerf Football and practice your approach. Hold the ball in your left hand and practice going thru the motion. This will get you acclimated to what the coach is teaching.

Understand that coaching is change and people are deathly afraid of change. There may be some major or minor changes that you will have to get used to. But when you get coaching, commit to that coach. The worst thing that you can do is have multiple coaches because not all coaches use the same method, not all coaches see the same thing.

Also, in the length of time you've havent been bowling, have you span checked and stats measured. The game has changed exponentially and it also doesnt hurt to know. I hope this all helps good luck and good bowling.

One thing you could try whilst setting up is to swing the ball back and forth, then bringing it back to the set position and immediately starting your pushaway and approach. The purpose of this would be to get something in motion to help trigger your start. I went from a 4-step to a 5-step approach last year because I had  similar trouble triggering my start. My first step is just to get my body in motion, then it's basically a 4-step approach from there. I found this much easier than trying to get everything moving at once.

So it seems like you are having trouble starting your swing. When you make that step the ball should be going in motion. As "Walking E." stated you might want to try the five step approach.

Don't give it up too quickly. It might take time. Stating from experience: I stopped bowling at the end of March and didn't pick up a bowling ball again until September.  That's 5 months off.  I have been practicing for almost 4 weeks now, and still haven't got things down. I couldn't imagine what it would be like after 17 years.
 
Just take your time and get that foot work down right. I am sure everything will come back eventually, you just have to practice. Just another helpful hint when you are practicing. Don't get caught up in your score, release, or accuracy Your primary focus is the foowork (good footwork is the foundation).