Hi there. I would look more at your soil condition. If it was in the ground and not doing well - no new shoots - your soil might be too heavy, maybe clay. Sunnier is good. If your soil is good I would plant this fall. Just my opinion. Lots of great gardeners here.
Thank you MomwithHope. The lilac is in a big barrel with potting soil, which I keep adding to as needed. So it is not in native soil. Have you ever heard of a lilac that doesn’t give out shoots? Maybe because it’s in a container, so that’s why I thought of putting it in the ground. I have a lot of lilacs, and have propagated a few very successfully. This particular one has sentimental value for me, so I’m trying to preserve and invigorate it.