If you are trying to play cross-platform (Ipad and Java on the computer), then it won't work. You have to play bedrock on bedrock or java on java.
I'm not certain of your specific circumstances, but occasionally another mob (usually a skeleton) accidentally shoots a creeper which causes it to blow up. In most cases, this is not a bug. Again though, its possible your circumstances are different
I just tested and this is an issue in both 1.16.4 and snapshot 20w51a. For my secondary test, I just created a superflat world with glass as the floor. Linked is a video of what I am experiencing.
I have this exact same issue, except that it happens no matter how I die. If I die by zombie, it does it, lava, it does it... etc. The way I get around it is: When I die, I go to spectator mode then exit out. It solves the issue.
Confirmed in 21w08b