My cpu its working but my acer monitor display after 5 min

Hello,

my cpu still running but my acer monitor display after 4 or 5 min after display never problem only starting problem waitting 4 or 5 min cpu still running because after monitor open in 5 min my screen show main desktop its mean cpu proper work but after 5 min wait destop on mointer after i open 6 to 8 hours not any problem after start monitor problem is only starting problem open my monitor some tim 3 or 4 or 5 min but i again restart pc open quickly only problem starting sry my english not good help