Atleast 5 possible things it could be.
Some inexpensive to fix, some expensive.
Generally, you should leave a tech checks things out on their own, after you tell them what it was doing, or not doing.
That way they are chasing wild guesses from over the internet. And charging you for wasting their time.
The safety is doing its job.
So its not overly dangerous(definition of overly?), but should be looked at ASAP.