I'm 72, use clipless pedals, and have never seen a hill I couldn't get started on. Straddling the bike with one pedal at about 10:00, push down on it and then put your foot on the second pedal. I don't see what could go wrong, unless you're in way too small or too large a gear. So the first thing to do is to shift into your startup gear before you stop. The trick of course is to know what that gear that is, which takes practice.

If you could do it fine last year but can't now. the problem is probably that you're not young but haven't yet realized that you start to lose strength if you don't work out for 3 days in a row. HTFU. Ride or workout at the gym somehow at least every other day. Ride the hills hard. Long out of the saddle climbing workouts are very good.

Oh, and switch to clipless pedals so you can use more of your leg muscles and pedal a higher cadence, but be careful with that. Practice lots on your trainer before you go out on the road. Don't have a trainer? It's time. Sometimes it rains or it's snowy and slick. Gotta keep it up year 'round. You can't do it on youth anymore.