Go around, twice on same trip

Flight MSP to MCO 12/29…wheels on the ground then engines fire up and back in the air. No explanation. Same trip TPA to MSP 1/5…ready to land and then engines fire back up, in the air again. This time there’s an announcement that there was a slow jet on the runway and to avoid collision we needed to do a go around. Very anxious flier, what the? I have travelled quite a bit over the last 40 years of my life and have never experienced a go around, let alone twice, same trip. What is going on? Is it air traffic control? So scary!