Without having your signal, I cannot provide specific code. To eliminate frequency-limited noise, I would use a bandstop filter with a stopband of 3 Hz to 4 Hz.
There are several ways to design filters in MATLAB, including dfilt and designfilt. My filter design procedure for IIR filters is here: How to design a lowpass filter for ocean wave data in Matlab? See the documentation for all the functions mentioned for an explanation of their options.