On my 1999 jeep wrangler [2.4L- 5spd] a circle w/a key in it appears on the upper left of the dash & it will start/run for a few seconds then shut down

I would think that it is an immobilizer symbol letting you know of a problem with the key in use
talk with a service dealer or have the fault codes read to see if there is an immobilizer fault

1999 , lost the operators guide?, best is to have one, so you can see each lights meaning.... (could save you or the car)
nah (check fuses first) then
try the 2nd key that came with car. lost that too?
SKIM light stuck on?
Skim lamp flashing.
before starting engine?

immo (SKIM) active does drop the ASD relay stalling engine, on all jeeps.
that is its job.
the FSM is free, and you can read how all that works there.

http://www.morris4x4center.com/knowledge-base/index.htm?utm_source=cj#service

btw2:
any scan tool will tell you why that lamp glows.
even bad key. or?

quote
The PCM uses the rolling
code algorithm to receive, decode and respond to the
valid/invalid key message sent by the SKIM. After
sending the valid/invalid key message the SKIM
waits 3.5 seconds for a PCM status message from
the PCM. If the PCM does not respond with a valid
key message to the SKIM, a fault is detected and a
trouble code is stored. The SKIS incorporates a
warning lamp located in the instrument cluster.
The lamp receives power and ground from the
instrument cluster. The lamp is actuated when the
SKIM sends a PCI Bus message to the instrument
cluster requesting the lamp on. The SKIM will
request warning lamp illumination for:
- bulb checks at ignition on
- to alert the vehicle operator to a SKIS malfunction
- customer key programming mode
For all faults except transponder faults and VIN
mismatch, the lamp remains on steady. In the event
of a transponder fault the light flashes at a rate of
1 Hz (once per second). If a fault is present the lamp
will remain on or flashing for the complete ignition
cycle. If a fault is stored in SKIM memory which
prevents the system from operating properly, the
PCM will allow the engine to start and run (for two
seconds) up to six times. After the sixth attempt the
PCM will not allow engine to start.