Amplifier auto standby mode when input signal removed

I’ve been using vacuum tube amplifiers off and on for quite a few years and recently observed a situation that I was not aware of. When the input signal is removed for an extended period the amplifier appears to go into standby mode automatically or at least that’s what it appears to be happening. When the input signal is reintroduced there it no amplification for about 30 seconds which seems to correspond to the “soft start” process. Also, during the time that it’s in the silent mode I didn’t measure the bias voltage but the temperature of the output tubes reduces to approximately 100° less (but not to room ambient temperature) than normal operating temperature. The amplifier under discussion is the Ayon Triton 1 that I very recently purchased used and I’m asking anyone who’s familiar with this amplifier to advise me if this is, indeed, it’s part of its design and, if this is the case, is it ok to leave the amp switched on even when not in use.