Started a daily flexibility routine - feeling unstable?

32 year old male - ignored flexibility and stretching for years. For the past two weeks I've done a daily stretching routine focusing on my legs and hips.

The poses are already a lot easier to do and I'm getting increased ROM but my whole abdominal section (lower back, abs, and glutes) just feels almost constantly unstable.

It feels weak and wobbly, a bit like if I put it under a little too much stress/did so without warming up it'd give way and pull. Is this a normal part of the process of loosening up a tight area? My hamstrings and hips have always been amazingly tight; I've never been able to touch my toes without bending my knees and I cannot do anything that looks like a downward dog.

So, is this normal? Or am I overdoing it?