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.
this could be due to a faulty cold start injector, or cold start injector time switch. Could also be caused by incorrect valve adjustment.
The 99 Blazer could be sluggish for several reasons. Check the air filter fuel pressure and EGR valve for a start.
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.