Are those some kind of timed-resetting fuses in DMMs?
[...] auto-reset after some time. Is this really true / possible ?


PTC fuses exhibit a behavior where they reset themselves over time.  When the current become too high, these fuses heat up and increase their resistance dramatically.  They become almost open circuits.  The fuses themselves do not get damaged by this, though.  When high current is removed, the fuses cool down over some time and return to the original low resistance.