Need help with panic attacks

Sometimes or often I have panic attacks that last for hours that will start for little or no reason

It can happen if I think of when I had a panic attack or being the centre of attention or if I’m sweating which then becomes a cycle where I’m panicking about sweating and sweating because I’m panicking but recently it’s been for no reason And I have been struggling to stop it

Anyone no why this is happening or know how to stop it? Thank you