Snapdragons germinate best if they are given a period of freezing. I stick my seed packages in the freezer for 3 or 4 days before planting. Snaps grow very slowly at first and do take a bit of time before plants are ready to flower. When to start depends on the variety. I start my dwarf snaps at the end of march and the taller ones a couple of weeks earlier for planting outside at the end of May. They are very frost tolerant--in fact they are a tender perennial--so as long as the ground is warm don't worry about them freezing. If the ground is not warm they will just sit there and may whither away. My snaps were still green at the end of November peeking above the snow and even in my zone 3 I have had some winter over.

Be careful of the germination temperature and light. Snaps germinate at 70-75 degrees and need light to germinate so don't cover them with soil

If you have a sunny protected area that warms up fast try gathering some seed in the fall and sprinkle it on the ground. I often have snaps reseed in my back south facing flowerbed by the house. If you stick a clear bottle with the bottom cut out and the lid removed over them it acts like a mini green house. Just make sure no leaves are touching the sides

thanks so much for your time and very informative answer!