Writing a bridge to a song is pretty hard. Well, its hard if you want it to be a true bridge rather than just some novelty change up. Simply changing rhythm or moving to some "minor chord" is not enough and its a stab in the dark at making a bridge what it could really truly be if you knew more about what you were doing.
It seems like you are wanting your bridge to break the monotony and take the song to a new height before returning back. If that is the case you are talking about "modulation". Modulation occurs when the song changes to a new key. NOT JUST GRABBING SOME NEW CHORDS. First you must establish tonality in the original key. Make sure the listener knows what key you are starting in. Then you can modulate correctly (powerfully, smoothly). Then for the modulation to sound true and strong you must establish tonality in the new key. Establish tonality by using alot of the I, V, III, and IV chords, or if using odd chords use alot of I, V, III, and IV notes in the melody. There are only a few kinds of modulation:
SHIFT MODULATION: This is the sleaziest and easiest. This is what most amateur songs have. Basically you just choose a new chord and go for it. It takes no skill and it shows. The only way a shift modulation can sound good is if the new key repeats the same chords like a sequential modulation. Alot of 60s music uses that kind of shift. Like when the whole verse and chorus moves up one fret for the end of the song.
SEQUENTIAL MODULATION: This is when a short melody repeats then repeats at a different pitch, carrying the song into the new key. Like in the song "When Love Comes Knocking at Your Door".
RELATIVE KEY MODULATION: This is when a song starts in a key, then changes to its relative major or minor. Like if you started in A, you would change the key to F#m, or from C to Am. Now be careful when doing it this way because relative chords are closely related anyways, so using secondary dominants will help make it obvious that the key is truly changing and not just using its relative casually like most songs do anyways. Remember, tonality must be established for the new key to be apparent to the listener.
PARALLEL KEY MODULATION: The song starts in a major or minor, then modulates to the major or minor of the same chord. For example, you start in A and end up in Am, or start in E and end up in Em. Alot of old Kinks tunes do this.
PIVOT CHORD MODULATION: The song changes to a new key using a chord common to both keys. This is another tricky one because tonality can be blurry if you dont watch out.
Modulation in chords has nothing to do with the beat or the rhythm. Unless you are changing the underlying meter of the song, the beats mean practically nothing. Simply adding more snare hits or something is not going to do anything UNLESS the modulation is solid from a harmonic perspective.
If you want to add a changing feeling try this (which you should be doing already if you are a skilled songwriter). You can make a song feel like its speeding up or slowing down by using augmentation or diminution of the melody rhythm. Meaning you just increase or decrease the number of notes you are singing from part to part. "Across the Universe" has a perfect example of how melodic augmentation and diminution work. You will also find it in a ton of other beatles tunes and practically every other great song as well.