If you don’t use the loop setting but rather use the sequencer to create a loop from a regular trig, you can use amp setup page AMP setting set to RTRG.
This will restart the envelope from zero every time the trig starts the loop again…
You can use the amp settings to adjust so it fades out too before it hits the trig and restarts again.
I think this is what your asking, there’s other ways to fade things in and out like the cross fader set to control xvol, or you could use an lfo… Probably more ways too… Trigless trigs and locks…