2000 Chevy Blazer

2000 Blazer, 80k miles. It doesnt like to start. It will just crank but not turn over, like the battery is weak (jumping it does not help). Then after a minute it will start to catch, RPM gauge will jump briefly, but then it stalls itself out like it is out of gas. Then I give up for 1/2 hour, go back and it starts right up after no more than 5-10 seconds. Then it runs (and re-starts) fine until it sits for another couple days.

This started 3 weeks ago, once the weather had dropped into the mid-30s and below.

I want to take it to be serviced, but dont know any trusted local mechanics and dont want to pay for "the works" if its just a spark plug or fuel filter issue.