Why is coffee comforting I find drinking coffee relaxes me. Given that caffeine is a stimulant, I would expect it to do the opposite. Why? is it psychological? does it have something to do with it being a hot beverage? is it an effect of the caffeine?
A 2008 U. Colorado (Boulder) study*, suggests that merely holding warm drinks (vs. cold) can positively influence perception of people. 

There is apparently some connection between the physical act of holding a warm drink and one's perception of the outside world. The association of warm beverages and positive feelings may underlie the sensation of relaxation as well, although I didn't find a study on precisely on point. 

Whether the effect is physiological or psychological the authors weren't sure.     

*Experiencing Physical Warmth Promotes Interpersonal Warmth, Science, 322: 606-607 (2008) Williams and Bargh.