If you look at it that you have a 3 card hand (any 3 cards) and you want to know the probability of getting those same cards dealt to you on the subsequent hand, then it is just equal to
(3/52) x (2/51) x (1/50) = 1/22100
which is just the probability of getting dealt any 3 specific cards (in any order). If you wanted to know the chances of getting those 3 cards dealt TWICE in a row it would be that value squared = 1/488410000
For example you start a game and play 2 hands - that value is the probability that you get dealt JQK of clubs in both hands.
For ANY two successive 3 card straight flushes (not necessarily the SAME straight flush - just 2 consecutive straight flushes) it is a little more complicated. First of all the value of 1/22100 indicates the probability of getting dealt ANY specific hand so that tells you there are a total of 22100 possible distinct 3 card poker hands (ignoring the ORDER dealt in). From this total of 22100, there are 48 possible straight flushes - 12 for each suit according to
A23,234,345,456,567,678,789,910J,10JQ,JQK,QKA
Therefore the possibility of getting a straight flush on any hand is just
48/22100
which is roughly
0.00217
Now to get 2 straight flushes in a row, would mean that we must square this value which is roughly
0.00000472
which is roughly
1/211984
I am fairly sure that the above is correct but I have had a considerable amount to drink so feel free to shoot it down....