Why won't the suburban start when I turn the key the security light comes on then goes off and if I wait long enough sometimes it'll beep a couple times and then I can turn the key in and start it but it hasn't been happening lately so what do I do

Hello, I can't think of anything that would prevent the key from turning to the start position other than the key or lock cylinder itself being compromised or worn out. If the security light goes out, and doesn't flash or anything like that, then there shouldn't be an immobilizer system issue. There could be a transmission shift lever position issue if it's not seeing "Park" or "Neutral" -- which would prevent cranking of the engine. Hands on inspection is needed to see what's going on. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops