If you're still a part of the Trusted Traveler program (GE, Pre, etc.) then you can probably rest assured you aren't on a no-fly list, or suspected of any nefarious connections.
SSSS is sometimes completely random. However, other aspects of your ticket or travel, anecdotally, result in a higher incidence of SSSS:
- One way tickets (especially if inbound to USA, with no checked bags and solo traveler)
- Tickets paid in cash
- Same-day bookings
- Travel to/from regions 'of concern' (or tickets issued by travel agents in such areas)
- Documentation discrepancies (incorrect
#s , non-matching names)
There are others too, but speaking from experience, the only times I've been subject to SSSS have been in cases like those I outline, plus once that I am convinced was totally random.