97 Jimmy ignition cuts out/briefly

New to AF and looking 4 possible fixes to try. 97 4.3..... As subject reads above.....(have done) put in new battery.....fuel pressure is always there but ignition cuts out. When COLD....it cranks hard and will shut down everything after approx 5 - 7 seconds of cranking. It does start after 2nd try. My (certified) mechanic says he might start at the crankshaft sensor. Truk will run fine at times but B4 I took it in....it cut out on the road for a second, after this all started a few weeks ago. Seems pronounced with cold weather or just when it cools down a few hours. Any common sensors to start with ? ? ? ? Thanks....Mark