Several things a weak battery , the terminals on the battery are not tight enough or a bad starter.
Several problems can cause a 1999 Blazer not to start. There could be a fuel problem or a firing problem. Check for fuel pressure and ignition spark first.
Could be in need of a tune up.
YES
Cheak fuel pression in the morning.
could be many reasons but the first one that comes to mind is a bad fuel pump.
Yes it sure can.
A bad engine temp sensor can do that.
The 99 Blazer could be sluggish for several reasons. Check the air filter fuel pressure and EGR valve for a start.
this could be due to a faulty cold start injector, or cold start injector time switch. Could also be caused by incorrect valve adjustment.
Dead starter?
You could have the start of a head gasket that is leaking. I suggest that you have a shop to add leak detector to the cooling system and check it with a black light.
A vacuum leak would do that. Check the base gasket under the throttle body.