what magnesium to take

okay so ill try to keep it as short as possible,

i have an active lifestyle and i have never taken any supplements, ive looked around a bit and saw that magnesium could really help in my situation.

i train kickboxing around 3/4 days a week and work 5days a week construction, i also do a bit of weight lifting but not much.

the thing is whem im doing nothing or when im about to sleep i feel sorta anxious and feel my heart pumping (i cant really explain the feeling) and i really dont like this.

does any of u know what kinda magnesium is good for me or if theres anything other that could help me with this.

and im not sure if this is the right sub to ask but thanks!