macbook 12 problem

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i have a 12 MacBook that ive had since new is a early 2015 model
sometimes when i login it boots up right away other times it lets me login opens up on the last page i was on then shuts down
other times it come up with the battery pic showing red like it needs to charge up so i plug in to mains and it comes on right away
when i look at battery charge it can be anything from 30 to 100 %
ive looked at the info about the battery cycle count 726 condition battery service recommended
does this mean i need a new battery fitted ?