As people have suggested, get your licence then sign up with an agency and do the odd weekend, or on your annual leave do a few days or a week.
I’m in the army and I do a day or 2 a week and on my 2 weeks leave I’ll do a weeks driving. It’s the best way to know if you’re making the right decision. I enjoy the job most of the time but in all honesty, after a year of fairly regular agency work I’m not sure i want to do it when I leave the military. I was dead set on it before. I think the total lack of advancement opportunities, the low pay, and all the ■■■■■■■■ and red tape that’s out there is off putting. I’m extremely torn as I do enjoy driving, I like being away from irritating people and when you deliver to a warehouse or something there’s no better feeling that knowing you’re leaving shortly and not stuck there like them, however to make a decent living in most driving jobs you’ve got to be putting in the 12-15 hour days.
Given your job, you’ve definitely got your head screwed on right, just thought I’d share my experience. You’re lucky that you have a regular salaried job currently, things are going to get painful for a lot of people soon, don’t make any rushed decisions!