Without knowing the miles/age of the car - I am guessing that your mounts are worn (as JRL said, mine were replaced at 90-110K on both cars).
However, a clunk after warm-up is likely not your mounts...if it were the mounts, it would clunk when cold too...sounds like a transmission issue...
2006 Corolla (kid's car - 108K, Conti Eco Contacts, Castrol Edge 5W30)
2005 MB S600 (63K, M1 0W40)
2002 V70-XC (165K, Nokian WR G2, Pennzoil Ultra 5W30)
2002 V70-T5 (143K, IPD bars, Bilsteins, Extreme Contact DWS, Mobil 1 5W40)
1992 MB 300E (Sportline - 123K, Nokian WR G2, Edge 5W40)
1990 4-Runner (V6, 4WD, mild lift - 239K, 31" BFG AT KO, Edge 10W30)
1932 Packard Sedan (straight 8, dual sidemount spares, original paint and interior, Shell Rotella 15W40)