Hypnosis doesn't necessarily feel like anything in particular, much like spending a little time on your computer doesn't seem like several hours have passed until you look at the clock. However, there are some spontaneous trance phenomena that are fairly common. 
Amnesia has been so frequently associated with trance that some people have the mistaken notion that if they remember what happened that they weren't in a trance. That's like thinking that the sun doesn't go down on cloudy days because there isn't any sunset. Although partial and complete amnesias do sometimes occur on their own, it's perfectly possible to remember trance experiences clearly. As a matter or fact, hypermesia, the opposite of amnesia, in which one remembers with exceptional detail, is another trance phenomenon. 
Sensory Distortions such as losing awareness of bodily sensations, or feeling that limbs are huge, heavy, or light can be part of a trance experience as well. These sensations are the same as those of someone half asleep, who struggles to move an arm or leg, because it seems like they're too heavy, or that it's just too much trouble. 
Catalepsy is simply staying comfortably still for extended periods of time. Frequently people in trance will sit unmoving in a hypnotist's chair for half an hour or longer, without noticing that they have been so still until it's pointed out to them later. That's simply because the mind is absorbed in other thoughts and sensations and they lose track of bodily awareness for a while. 
Time Distortion, in which the subjective experience of time is different from the clock, is common when in a trance. Frequently thirty minutes in hypnosis will seem like only five or ten minutes. 
Trance may include awareness of any, all, or none of the above.  The thing to remember, as you experience trance, is to forget to be concerned about whether you're aware or not of any trance phenomena, because it's possible to be doing them outside of awareness. Time distortion, for example, is usually only recognized after the fact. The more you go in and out of trances, the more you'll be able to recognize the internal signals that let you know that you're there, and so just let go and enjoy the process of learning more about your unconscious.