Post Exercise, or 'Recovery' PVC and PAC are extremely common and a perfectly normal finding.
As with any PVC issue, different people react to PVC's differently. You just happen to fall into the class of people that tend to feel them and be bothered.
Truth is, probably 80% of everyone else in the gym has the same problem and just never notices it.
Yes I get them, I mainly get them at rest but I also get them during cool down from hard exercise primarily when my breathing slows from quick down to deep full gasps and I stop moving around at all - they will 90% of them time fire off at the very top of a deep breath.
When I get into better shape they go away. Mine are PACs.